how do bacteria metabolize

All microbial metabolisms can be arranged according to three principles:

• 1. How the organism obtains carbon for synthesizing cell mass: [1] autotrophic – carbon is obtained from carbon dioxide (CO 2) ...
• 2. How the organism obtains reducing equivalents (hydrogen atoms or electrons) used either in energy conservation or in biosynthetic reactions: lithotrophic – reducing equivalents are obtained from inorganic compounds ...
• 3. How the organism obtains energy for living and growing:

Full Answer

What are kinds of metabolism does bacteria use?

Do Bacteria Cells Use Energy? For bacteria of the heterotrophic (or organotrophic) family, they are required to obtain both carbon and energy through organic molecules. Cell energy can be generated in two ways through sugar metabolism: in fermentation and through respiration.

What is true about metabolism in all organisms?

Metabolism is the total amount of the biochemical reactions involved in maintaining the living condition of the cells in an organism. All living organisms require energy for different essential processes and for producing new organic substances. The metabolic processes help in growth and reproduction and help in maintaining the structures of ...

What is the role of metabolism in living organisms?

Metabolism refers to the whole sum of reactions that occur throughout the body within each cell and that provide the body with energy. This energy gets used for vital processes and the synthesis of new organic material. Every living organism uses its environment to survive by taking nutrients and substances that act as building blocks for movement, growth, development, and reproduction.

What can bacteria metabolize?

To establish a carbon-neutral circular economy in the future, technologies are needed that use carbon dioxide as a raw material. In the form of formate, CO2 can be metabolized by certain bacteria. Acetogens are a group of bacteria that can metabolize formate. For example, they form acetic acid – an important basic chemical.

How do bacteria regulate their metabolism?

They regulate their metabolism to adapt to the ever-changing environment. Since almost all biological reactions are catalyzed by enzymes, metabolism is regulated by controlling the synthesis of enzymes and their activity (Table 12.1).

Can bacteria metabolize and use energy?

Bacteria can gain energy by a number of processes: aerobic respiration, anaerobic respiration, fermentation and photosynthesis. In all these processes energy-yielding metabolism is coupled to the formation of ATP.

How do microbes use metabolism?

By metabolizing such substances, microbes chemically convert them to other forms. In some cases, microbial metabolism produces chemicals that can be harmful to other organisms; in others, it produces substances that are essential to the metabolism and survival of other life forms (Figure 8.

How do bacteria consume energy?

Bacteria can obtain energy and nutrients by performing photosynthesis, decomposing dead organisms and wastes, or breaking down chemical compounds. Bacteria can obtain energy and nutrients by establishing close relationships with other organisms, including mutualistic and parasitic relationships.

What are primary metabolites in bacteria?

Primary metabolites include amino acids, nucleotides, and fermentation end products such as ethanol and organic acids, which are considered essential for proper growth of microorganisms.

What affects bacterial metabolism?

Water temperature alone had the greatest effect on bacterial metabolism (Table 2). BR increased with increasing temperatures while BP slightly decreased with increasing temperatures. Consequently BGE decreased with increasing temperatures mainly related to the highest BR in the highest incubation temperatures.

How do bacteria get energy without mitochondria?

Answer and Explanation: Bacteria produce energy in essentially the same way as the cells in eukaryotes. Lacking mitochondria however they create a proton gradient along their cellular membrane by pumping protons out of the cell. This gradient then allows them to produce ATP as the protons re-enter the cell.

What are the 4 metabolic processes?

Green nodes: lipid metabolism.Catabolic pathway (catabolism)Anabolic pathway (anabolism)Amphibolic pathway.

Can prokaryotes metabolize energy?

Prokaryotes may perform aerobic (oxygen-requiring) or anaerobic (non-oxygen-based) metabolism, and some can switch between these modes. Some prokaryotes have special enzymes and pathways that let them metabolize nitrogen- or sulfur-containing compounds.

Do viruses metabolize and use energy?

Viruses themselves are metabolically inert and must rely on metabolic events in the cell to generate its component parts and to replicate new viral copies. Oftentimes, the cell at the time of infection is in a quiescent state, but the infection acts to change the cell's metabolic activity.

Can microbes also be used as a source of energy?

Yes, Microbes can be used as a source of energy. Gober gas is a mixture of methane (CH4), carbon dioxide (CO2), hydrogen (H2) and hydrogen sulphide (H2S) with methane as a major component (65%). Methanogens are anaerobic autotrophic bacteria that convert carbon dioxide and hydrogen into methane gas.

Are microbes can be used as a source of energy?

For energy production, microbes offer efficient and sustainable ways to convert plants or other biomass into liquid fuels, hydrogen, methane, electricity, or chemical feedstocks currently derived from fossil fuels.

How does anaerobic metabolism work?

Anaerobic metabolism is when metabolic pathways are carried out in the absence of oxygen. It works by breaking down chemicals to generate other che...

What is the end product of anaerobic metabolism?

The end products of anaerobic metabolism depends on the bacteria carrying out the metabolism and the beginning chemical compound. Some end products...

Where does anaerobic metabolism occur?

Anaerobic metabolism is metabolism that takes place in the absence of oxygen. It can occur anywhere where oxygen is not present such as the deep oc...

How do anaerobic bacteria grow?

Anaerobic bacteria are the bacteria that are able to grow in the absence of oxygen. They grow by using anaerobic bacterial metabolism to produce th...

Why do bacteria use respiration?

Bacteria that are able to use respiration produce far more energy per sugar molecule than do fermentative cells, because the complete oxidation (breakdown) of the energy source allows complete extraction of all of the energy available as shown by the substantially greater yield of ATP for respiring organisms than for fermenting bacteria.

Why do fermentative bacteria produce large quantities of organic end products?

Because organic molecules are only partially oxidized during fermentation, the growth of fermentative bacteria results in the production of large quantities of organic end products and a relatively small output of energy per glucose molecule consumed.

How does sugar metabolism work?

Sugar metabolism produces energy for the cell via two different processes, fermentation and respiration. Fermentation is an anaerobic process that takes place in the absence of any external electron acceptor. The organic compound, such as a sugar or amino acid, is broken down into smaller organic molecules, which accept the electrons that had been released during the breakdown of the energy source. These catabolic reactions include a few steps that result in the direct formation of ATP. When glucose is broken down to lactic acid, as occurs in some Lactococcus and Lactobacillus species, as well as in muscle cells in higher eukaryotes, each molecule of glucose yields only two molecules of ATP, and considerable quantities of glucose must be degraded to provide sufficient energy for bacterial growth. Because organic molecules are only partially oxidized during fermentation, the growth of fermentative bacteria results in the production of large quantities of organic end products and a relatively small output of energy per glucose molecule consumed. Few bacteria produce only lactic acid, which is fairly toxic for bacteria and limits the growth of a colony. A variety of additional fermentation pathways are used by specific bacteria to break down glucose; the characteristic end products of these pathways assist in the identification of the bacteria. These end products are often less toxic than lactic acid or are formed with the harnessing of additional metabolic energy. For example, the products of mixed-acid fermentation in E. coli include lactic acid, succinic acid, acetic acid, formic acid, ethyl alcohol, carbon dioxide, and hydrogen gas. Enterobacter aerogenes produces most of the same set of fermentation products, as well as large amounts of 2,3-butylene glycol, which is nonacidic and permits more bacterial growth.

What is the final electron acceptor of anaerobic respiration?

Respiration can also occur under anaerobic conditions by processes called anaerobic respiration, in which the final electron acceptor is an inorganic molecule, such as nitrate (NO 3− ), nitrite (NO 2− ), sulfate (SO 42− ), or carbon dioxide (CO 2 ).

How many molecules of ATP does glucose produce?

When glucose is broken down to lactic acid, as occurs in some Lactococcus and Lactobacillus species, as well as in muscle cells in higher eukaryotes, each molecule of glucose yields only two molecules of ATP, and considerable quantities of glucose must be degraded to provide sufficient energy for bacterial growth.

How does respiration generate energy?

Considerably more energy is available to the cell from respiration, a process in which the electrons from molecules of sugar are transferred not to another organic molecule but to an inorganic molecule. The most familiar respiratory process ( aerobic respiration) uses oxygen as the final electron acceptor. The sugar is completely broken down to carbon dioxide and water, yielding a maximum of 38 molecules of ATP per molecule of glucose. Electrons are transferred to oxygen using the electron transport chain, a system of enzymes and cofactors located in the cell membrane and arranged so that the passage of electrons down the chain is coupled with the movement of protons ( hydrogen ions) across the membrane and out of the cell. Electron transport induces the movement of positively charged hydrogen ions to the outside of the cell and negatively charged ions to its interior. This ion gradient results in the acidification of the external medium and an energized plasma membrane with an electrical charge of 150 to 200 millivolts. The generation of ion gradients, including this protonmotive force (gradient of protons), is a common aspect of energy generation and storage in all living organisms. The gradient of protons is used directly by the cell for many processes, including the active transport of nutrients and the rotation of flagella. The protons also can move from the exterior of the cell into the cytoplasm by passing through a membrane enzyme called the F 1 F 0 -proton-translocating ATPase, which couples this proton movement to ATP synthesis in a process identical to that which occurs in the mitochondria of eukaryotic cells ( see metabolism: The combustion of food materials ).

What is heterotrophic metabolism?

Heterotrophic metabolism. As stated above, heterotrophic (or organotrophic) bacteria require organic molecules to provide their carbon and energy. The energy-yielding catabolic reactions can be of many different types, although they all involve electron-transfer reactions in which the movement of an electron from one molecule to another is coupled ...

What is the primary chemical energy source for bacteria?

Bacteria, like mammalian and plant cells, use ATP or the high-energy phosphate bond (~ P) as the primary chemical energy source. Bacteria also require the B-complex vitamins as functional coenzymes for many oxidation-reduction reactions needed for growth and energy transformation.

What is the energy of a bacterial cell?

The bacterial cell is a highly specialized energy transformer. Chemical energy generated by substrate oxidations is conserved by formation of high-energy compounds such as adenosine diphosphate (ADP) and adenosine triphosphate (ATP) or compounds containing the thioester bond

What are the similarities between bacteria and other living organisms?

Kluyver and Donker (1924 to 1926) recognized that bacterial cells, regardless of species, were in many respects similar chemically to all other living cells. For example, these investigators recognized that hydrogen transfer is a common and fundamental feature of all metabolic processes. Bacteria, like mammalian and plant cells, use ATP or the high-energy phosphate bond (~ P) as the primary chemical energy source. Bacteria also require the B-complex vitamins as functional coenzymes for many oxidation-reduction reactions needed for growth and energy transformation. An organism such as Thiobacillus thiooxidans, grown in a medium containing only sulfur and inorganic salts, synthesizes large amounts of thiamine, riboflavine, nicotinic acid, pantothenic acid, pyridoxine, and biotin. Therefore, Kluyver proposed the unity theory of biochemistry ( Die Einheit in der Biochemie ), which states that all basic enzymatic reactions which support and maintain life processes within cells of organisms, had more similarities than differences. This concept of biochemical unity stimulated many investigators to use bacteria as model systems for studying related eukaryotic, plant and animal biochemical reactions that are essentially "identical" at the molecular level.

What is the term for the biochemical reactions that occur in a cell or organism?

Metabolism refers to all the biochemical reactions that occur in a cell or organism. The study of bacterial metabolism focuses on the chemical diversity of substrate oxidations and dissimilation reactions (reactions by which substrate molecules are broken down), which normally function in bacteria t …. Metabolism refers to all the biochemical ...

What is the name of the organism that synthesizes thiamine?

An organism such as Thiobacillus thiooxidans, grown in a medium containing only sulfur and inorganic salts, synthesizes large amounts of thiamine, riboflavine, nicotinic acid, pantothenic acid, pyridoxine, and biotin.

What are the three types of bacteria?

From a nutritional, or metabolic, viewpoint, three major physiologic types of bacteria exist: the heterotrophs (or chemoorganotrophs), the autotrophs (or chemolithotrophs), and the photosynthetic bacteria (or phototrophs) (Table 4-1). These are discussed below.

Who recognized that bacterial cells are similar to all other living cells?

Kluyver and Donker (1924 to 1926) recognized that bacterial cells, regardless of species, were in many respects similar chemically to all other living cells. For example, these investigators recognized that hydrogen transfer is a common and fundamental feature of all metabolic processes.

How do antibiotics affect bacteria?

1. Antibiotics alter the metabolic state of bacteria, which contributes to the resulting death or stasis; 2. The metabolic state of bacteria influences their susceptibility to antibiotics; and. 3. Antibiotic efficacy can be enhanced by altering the metabolic state of bacteria.

Why is metabolic activity important for antibiotics?

Since the metabolic state of bacteria is a unifying feature defining antibiotic efficacy across a wide range of physiologic states, this greatly simplifies the search for mechanisms through which bactericidal antibiotic activity can be enhanced. Indeed, rather than necessitating the identification of functionally unique adjuvant methods for each specific physiologic state in which a bacterium may exist, modulating metabolic activity is a generalizable approach to enhance bactericidal drug-dependent killing (Figure 3).

What are the characteristics of antibiotic tolerant bacteria?

Antibiotic-tolerant bacteria—whether nutrient-limited stationary phase cells, persisters, or biofilms— all display repressed metabolism that contributes to their ability to survive bactericidal antibiotic treatment. Metabolic activation through the use of metabolite adjuvants has been shown to enhance the sensitivity of antibiotic-tolerant bacteria to conventional bactericidal antibiotics. Furthermore, molecules like polymyxins, human cationic peptides, and ADEP4 display bactericidal activity that is independent of the metabolic state of the cell and may represent a promising approach to develop antibiotics that are not impeded by metabolic repression displayed by conventionally antibiotic-tolerant populations. Lastly, engineered phage and bacteria that actively modulate the metabolic response of pathogens to conventional antibiotics may be an alternative approach to eradicate cells in metabolically repressed states.

What are the metabolic consequences of antibiotics?

In this perspective, we emphasize the importance of these metabolic consequences of antibiotic treatment by describing three postulates that define antibiotic efficacy in the context of bacterial metabolism: 1. Antibiotics alter the metabolic state of bacteria, which contributes to the resulting death or stasis; 2.

What influences bacteria's susceptibility to antibiotics?

The Metabolic State of Bacteria Influences Their Susceptibility to Antibiotics

What are the four primary biosynthesis processes?

With few exceptions, target processes can be grouped into four primary categories: cell envelope biogenesis, DNA replication, transcription, and protein biosynthesis.

Do antibiotics cause cell death?

Altogether, these observations are consistent with a model where primary target corruption by bactericidal antibiotics results in collateral damage to intracellular macromolecules, inducing a cycle of elevated stress responses and concurrently increased metabolic activity, which terminates with cell death (Figure 2). Importantly, this generalized model is consistent with seminal work by Cho et al., which revealed that the β-lactam antibiotic mecillinam induces an energy-demanding futile cycle of cell wall biosynthesis and degradation that depletes cellular resources (Cho et al., 2014), thereby increasing the metabolic rate that contributes to lethality. Similarly, it has been shown that genetically inducing ATP-consuming futile cycles in E. colithrough the expression of pck, acs, and atpAGDsignificantly sensitizes cells to killing by exogenous oxidative stress (Adolfsen and Brynildsen, 2015). Recent work has additionally shown that bactericidal antibiotics of wide-ranging functions continue to induce reactive oxygen species accumulation and death of E. colieven after their removal from cells (Hong et al., 2019). While the precise mechanism underlying this self-amplifying accumulation of reactive molecules remains to be determined, ongoing work will likely shed light on the energy-dependent cycles that increase metabolic activity and macromolecule damage, which contribute to bacterial cell killing upon exposure to bactericidal compounds.

What is the metabolic model of a bacterial cell?

This is the process of aerobic respiration, or the process in which a compound is oxidized using oxygen as the terminal electron acceptor and resulting in a proton motive force.

How does glycolysis work?

First, the cell will use glycolysis to strip glucose of its electrons, breaking it down into pyruvate and capturing the electrons on the electron carrier NADH. The pyruvate then enters the citric acid cycle, where it is oxidized all the way to carbon dioxide.

What is anaerobic respiration?

The answer is by using processes like anaerobic respiration, which is breathing or respiring something besides oxygen, and fermentation. In this lesson, we will discuss the details of anaerobic respiration.

How does ATP synthase work?

The ATP synthase opens a channel through the membrane and, as the protons flow through the channel down the gradient, the energy turns the ATP synthase, resulting in a torque force that is used to add a phospha te group to ADP to generate ATP.

How many bacteria are there in the human body?

There are trillions of bacterial cells living in association with your body, outnumbering human cells by 10 times. Bacteria are able to pull off this amazing feat of world domination by having metabolic abilities that allow them to survive in some pretty crazy environments.

Does the sulfate reducing electron transport chain have an obvious link to the glycolysis and citric acid?

But if you look closely, you will see that the sulfate-reducing electron transport chain does not have an obvious link to the glycolysis and citric acid cycle components. In fact, most of the cells use pyruvate, lactate, or hydrogen as their electron donor, and the enzymes required for this are embedded right in the electron transport chain.

Can bacteria grow without oxygen?

Bacteria are metabolically versatile and can grow in a range of environments. Many bacteria grow in environments without oxygen using anaerobic respiration and fermentation. This lesson will discuss the process of anaerobic respiration in bacteria. Create an account.

Which enzymes are involved in the metabolic pathway of alkanes?

The first enzymes in the metabolic pathways of alkanes are monooxygenases, while aromatic hydrocarbons are attacked by either monooxygenases or dioxygenases. These enzymes incorporate hydroxyl groups, derived from molecular oxygen, into the aliphatic chain or the aromatic ring.

When was the first pure culture of an alkane-degrading bacterium?

The first pure culture of an alkane-degrading bacterium was reported in 1991. This bacterium, sulfate-reducing strain Hxd3, grows on hexadecane and other long chain alkanes under strictly anaerobic conditions. The degradation balance showed that hexadecane was completely oxidized to CO 2 at the expense of sulfate [29]. Since then, several further sulfate-reducing alkane-degrading isolates have been obtained which grow on alkanes with chains of six and more carbon atoms [ 30, 31 ]. The known alkane-degrading sulfate-reducing bacteria are nutritionally and phylogenetically unrelated to Desulfovibrio species [30]. The biochemical basis of hydrocarbon metabolism in these organisms is still poorly understood. Experiments with cell suspensions have indicated that anaerobic alkane degradation probably does not occur via dehydrogenation to a 1-alkene and hydration to an alcohol [30], a hypothetical mechanism presented in former literature. Most interestingly, one of the isolated alkane-degrading sulfate reducers, strain Hxd3 ( Table 2 ), was found to produce membrane lipids containing odd numbers of C-atoms from alkanes with an even number of C-atoms (and vice versa). In contrast, control cells grown on 1-alkenes or fatty acids did not show this shift in the carbon chain length of cellular fatty acids. This indicates that alkanes and alkenes have different metabolic routes in this strain, and that addition or removal of a metabolite containing an odd number of C-atoms is involved in anaerobic alkane catabolism. The most plausible explanation for this would involve an initial carboxylation or carbonylation of the activated alkane to produce the C n+1 -fatty acid or aldehyde [30]; this would formally correspond to a reversal of the assumed biosynthetic reactions involved in alkane biosynthesis [5]. However, the described alteration of the chain length of fatty acids upon growth on alkanes has not been observed in any of the other known strains capable of growing anaerobically on alkanes (see Table 2 ). This suggests that there are different mechanisms for initiating anaerobic alkane metabolism, and that the mechanism employed depends on the bacterial strain [30].

How does benzylsuccinate synthase work?

The proposed reaction mechanism of benzylsuccinate synthase begins with the radical-containing, activated form of the enzyme ( Fig. 3 ). It appears plausible that an enzyme-based radical of active benzylsuccinate synthase first abstracts a hydrogen atom from toluene to yield a benzyl radical at the active site. This radical would then add to the double bond of fumarate, forming a benzylsuccinyl radical. This type of radical addition to a C–C double bond is well known in organic chemistry and is employed in free-radical polymerization reactions [4]. Finally, the enzyme would donate the abstracted hydrogen atom back to the benzylsuccinyl radical, thus forming benzylsuccinate and at the same time regenerating the enzyme radical ( Fig. 3 ). The strong homology to pyruvate formate-lyase suggests that the glycyl radical may react with the conserved cysteine residue to form an intermediate thiyl radical, which actually abstracts the hydrogen atom.

What are the mechanisms of hydrocarbons?

Radical mechanisms are also involved in some known oxygen-independent chemical reactions of hydrocarbons. Alkanes and alkyl side chains of aromatic hydrocarbons can be chemically ‘cracked’ to smaller alkanes and alkenes by pyrolysis, or halogenated with elemental halogens in the presence of light. Both reactions involve free radical intermediates. These reactions are technically performed under conditions which are not compatible with biological systems. Yet, it was recently elucidated that some bacteria actually employ oxygen-independent radical reactions to make hydrocarbons available as substrates (see below).

How do hydrocarbons conserve energy?

Hydrocarbons are highly reduced organic molecules. In chemotrophic organisms, the reducing equivalents generated during transformation of hydrocarbons to metabolic intermediates need to be transferred to an electron acceptor with a more positive redox potential to allow energy conservation for growth. Based on our present biochemical knowledge, energy conservation from hydrocarbon metabolism by a chemotrophic organism in pure culture is not conceivable in the absence of an external electron acceptor. In the absence of oxygen as terminal electron acceptor, energy conservation may be accomplished by anaerobic respiration with nitrate, ferric iron or sulfate ( Table 1 ). Accordingly, all anaerobic hydrocarbon degrading strains, which are available as pure cultures, are either denitrifying, ferric iron-reducing or sulfate-reducing bacteria ( Table 2 ). In addition, some bacteria may dispose of the reducing equivalents recovered from hydrocarbon oxidation by reducing protons to hydrogen, but this is thermodynamically feasible only in syntrophic association with hydrogen-consuming microorganisms, such as methanogens (see below). None of the ‘proton-reducing’ hydrocarbon-degrading bacteria is available in a defined coculture or in pure culture. A last group of anaerobic bacteria, which may principally use hydrocarbons as carbon- and electron sources, are the anoxygenic photosynthetic bacteria. However, although these bacteria are long known to metabolize polar aromatic compounds, no hydrocarbon-metabolizing phototrophic bacteria are yet reported.

Where are hydrocarbons found in the environment?

Hydrocarbon compounds as substrates for aerobic and anaerobic bacteria have probably always been available near natural petroleum deposits or petroleum formation sites, e.g. the Guaymas Basin [65]. Since one can assume continuous spreading of hydrocarbons into anaerobic environments over geological periods, the existence of bacteria capable of anaerobic hydrocarbon degradation is understandable from an ecological standpoint. In modern environments, polluted by human activity, these organisms are probably enriched, together with the long-known aerobic hydrocarbon degraders thriving in the oxic zones.

Can bacteria metabolize hydrocarbons?

The capacity of some bacteria to metabolize hydrocarbons in the absence of molecular oxygen was first recognized only about ten years ago. Since then, the number of hydrocarbon compounds shown to be catabolized anaerobically by pure bacterial cultures has been steadily increasing. This review summarises the current knowledge ...

What is the name of the type of microbial metabolism that uses hydrogen as an electron donor?

Main article: Acetogenesis. Acetogenesis is a type of microbial metabolism that uses hydrogen ( H. 2) as an electron donor and carbon dioxide ( CO. 2) as an electron acceptor to produce acetate, the same electron donors and acceptors used in methanogenesis (see above).

What is the term for the process by which a microbe obtains the energy and nutrients it needs to live and?

Please consider expanding the lead to provide an accessible overview of all important aspects of the article. (December 2020) Microbial metabolism is the means by which a microbe obtains the energy and nutrients (e.g. carbon) it needs to live and reproduce.

Why are fermentative organisms important?

Fermentative organisms are very important industrially and are used to make many different types of food products. The different metabolic end products produced by each specific bacterial species are responsible for the different tastes and properties of each food.

What is syntrophy in biology?

Syntrophy, in the context of microbial metabolism, refers to the pairing of multiple species to achieve a chemical reaction that, on its own, would be energetically unfavorable. The best studied example of this process is the oxidation of fermentative end products (such as acetate, ethanol and butyrate) by organisms such as Syntrophomonas. Alone, the oxidation of butyrate to acetate and hydrogen gas is energetically unfavorable. However, when a hydrogenotrophic (hydrogen-using) methanogen is present the use of the hydrogen gas will significantly lower the concentration of hydrogen (down to 10 −5 atm) and thereby shift the equilibrium of the butyrate oxidation reaction under standard conditions (ΔGº’) to non-standard conditions (ΔG’). Because the concentration of one product is lowered, the reaction is "pulled" towards the products and shifted towards net energetically favorable conditions (for butyrate oxidation: ΔGº’= +48.2 kJ/mol, but ΔG' = -8.9 kJ/mol at 10 −5 atm hydrogen and even lower if also the initially produced acetate is further metabolized by methanogens). Conversely, the available free energy from methanogenesis is lowered from ΔGº’= -131 kJ/mol under standard conditions to ΔG' = -17 kJ/mol at 10 −5 atm hydrogen. This is an example of intraspecies hydrogen transfer. In this way, low energy-yielding carbon sources can be used by a consortium of organisms to achieve further degradation and eventual mineralization of these compounds. These reactions help prevent the excess sequestration of carbon over geologic time scales, releasing it back to the biosphere in usable forms such as methane and CO#N#2 .

What is the purpose of fermentation?

Fermentation is a specific type of heterotrophic metabolism that uses organic carbon instead of oxygen as a terminal electron acceptor. This means that these organisms do not use an electron transport chain to oxidize NADH to NAD+#N#and therefore must have an alternative method of using this reducing power and maintaining a supply of NAD+#N#for the proper functioning of normal metabolic pathways (e.g. glycolysis). As oxygen is not required, fermentative organisms are anaerobic. Many organisms can use fermentation under anaerobic conditions and aerobic respiration when oxygen is present. These organisms are facultative anaerobes. To avoid the overproduction of NADH, obligately fermentative organisms usually do not have a complete citric acid cycle. Instead of using an ATP synthase as in respiration, ATP in fermentative organisms is produced by substrate-level phosphorylation where a phosphate group is transferred from a high-energy organic compound to ADP to form ATP. As a result of the need to produce high energy phosphate-containing organic compounds (generally in the form of Coenzyme A -esters) fermentative organisms use NADH and other cofactors to produce many different reduced metabolic by-products, often including hydrogen gas ( H#N#2 ). These reduced organic compounds are generally small organic acids and alcohols derived from pyruvate, the end product of glycolysis. Examples include ethanol, acetate, lactate, and butyrate. Fermentative organisms are very important industrially and are used to make many different types of food products. The different metabolic end products produced by each specific bacterial species are responsible for the different tastes and properties of each food.

What are the microbes that use light as a source of energy?

Many microbes (phototrophs) are capable of using light as a source of energy to produce ATP and organic compounds such as carbohydrates, lipids, and proteins. Of these, algae are particularly significant because they are oxygenic, using water as an electron donor for electron transfer during photosynthesis. Phototrophic bacteria are found in the phyla Cyanobacteria, Chlorobi, Proteobacteria, Chloroflexi, and Firmicutes. Along with plants these microbes are responsible for all biological generation of oxygen gas on Earth. Because chloroplasts were derived from a lineage of the Cyanobacteria, the general principles of metabolism in these endosymbionts can also be applied to chloroplasts. In addition to oxygenic photosynthesis, many bacteria can also photosynthesize anaerobically, typically using sulfide ( H#N#2S) as an electron donor to produce sulfate. Inorganic sulfur ( S#N#0 ), thiosulfate ( S#N#2O2−#N#3) and ferrous iron ( Fe2+#N#) can also be used by some organisms. Phylogenetically, all oxygenic photosynthetic bacteria are Cyanobacteria, while anoxygenic photosynthetic bacteria belong to the purple bacteria (Proteobacteria), Green sulfur bacteria (e.g. Chlorobium ), Green non-sulfur bacteria (e.g. Chloroflexus ), or the heliobacteria (Low %G+C Gram positives). In addition to these organisms, some microbes (e.g. the Archaeon Halobacterium or the bacterium Roseobacter, among others) can utilize light to produce energy using the enzyme bacteriorhodopsin, a light-driven proton pump. However, there are no known Archaea that carry out photosynthesis.

What are some examples of methylotrophs?

Several other less common substrates may also be used for metabolism, all of which lack carbon-carbon bonds. Examples of methylotrophs include the bacteria Methylomonas and Methylobacter. Methanotrophs are a specific type of methylotroph that are also able to use methane ( CH#N#4) as a carbon source by oxidizing it sequentially to methanol ( CH#N#3OH ), formaldehyde ( CH#N#2O ), formate ( HCOO−#N#), and carbon dioxide CO#N#2 initially using the enzyme methane monooxygenase. As oxygen is required for this process, all (conventional) methanotrophs are obligate aerobes. Reducing power in the form of quinones and NADH is produced during these oxidations to produce a proton motive force and therefore ATP generation. Methylotrophs and methanotrophs are not considered as autotrophic, because they are able to incorporate some of the oxidized methane (or other metabolites) into cellular carbon before it is completely oxidized to CO#N#2 (at the level of formaldehyde), using either the serine pathway ( Methylosinus, Methylocystis) or the ribulose monophosphate pathway ( Methylococcus ), depending on the species of methylotroph.

What are the elements that bacteria secrete?

These include sources of organic carbon, nitrogen, phosphorus, sulfur and metal ions including iron. Bacteria secrete small molecules that bind iron (siderophores, e.g. enterobactin, mycobactin). Siderophores (with bound iron) are then internalized via receptors by the bacterial cell. The human host also has iron transport proteins (e.g. transferrin). Thus bacteria that ineffectively compete with the host for iron are poor pathogens.

What are the three things that bacteria need to grow?

BACTERIOLOGY - CHAPTER THREE. Bacterial requirements for growth include sources of energy, "organic" carbon (e.g. sugars and fatty acids) and metal ions (e.g. iron). Optimal temperature, pH and the need (or lack of need for oxygen) are important.

What is the process of converting NAD to NADH?

Aerobic Respiration. Aerobic Respiration involves glycolysis and the tricarboxylic acid cycle (Krebs cycle). Pyruvate is fully broken down to carbon dioxide (C1) and in the process, NAD is converted to NADH. Thus, in aerobic fermentation, NADH is generated from two sources (glycolysis and the Krebs cycle).

How is NADH generated in aerobic fermentation?

Thus, in aerobic fermentation, NADH is generated from two sources (glycolysis and the Krebs cycle). Oxidative phosphorylation converts excess NADH back to NAD and in the process produces more ATP (stored energy). Ubiquinones and cytochromes are components of the electron transport chain involved in this latter process.

How many intermediates are in the Krebs cycle?

The Krebs cycle (Figure 2) contains 4 and 6 carbon intermediates. Pyruvate (C3) can feed into the Krebs cycle in such a way that the number of C4/C6 intermediates remains the same or increases.

How are fatty acids broken down?

Fatty acids are broken down to acetyl groups (C2) which feed into the Krebs Cycle by addition to a C4 intermediate to produce C6. During the cycle, the added C2 is lost as CO 2 and C4 regenerated. Overall, no increase in the number of molecules of cycle intermediates occurs. Thus, if fatty acids are the sole carbon source, no Krebs cycle intermediates can be removed without shutting it down:

What is the pathway of sugar catabolism?

This is the most common pathway in bacteria for sugar catabolism (It is also found in most animal and plant cells). A series of enzymatic processes result in conversion of sugars into pyruvate, generating ATP (adenosine triphosphate) and NADH (nicotinamide adenine dinucleotide).

What are the elements that bacteria secrete?

These include sources of organic carbon, nitrogen, phosphorus, sulfur and metal ions including iron. Bacteria secrete small molecules that bind iron (siderophores, e.g. enterobactin, mycobactin). Siderophores (with bound iron) are then internalized via receptors by the bacterial cell. The human host also has iron transport proteins (e.g. transferrin). Thus bacteria that ineffectively compete with the host for iron are poor pathogens.

What are the three things that bacteria need to grow?

BACTERIOLOGY - CHAPTER THREE. Bacterial requirements for growth include sources of energy, "organic" carbon (e.g. sugars and fatty acids) and metal ions (e.g. iron). Optimal temperature, pH and the need (or lack of need for oxygen) are important.

What is the process of converting NAD to NADH?

Aerobic Respiration. Aerobic Respiration involves glycolysis and the tricarboxylic acid cycle (Krebs cycle). Pyruvate is fully broken down to carbon dioxide (C1) and in the process, NAD is converted to NADH. Thus, in aerobic fermentation, NADH is generated from two sources (glycolysis and the Krebs cycle).

How is NADH generated in aerobic fermentation?

Thus, in aerobic fermentation, NADH is generated from two sources (glycolysis and the Krebs cycle). Oxidative phosphorylation converts excess NADH back to NAD and in the process produces more ATP (stored energy). Ubiquinones and cytochromes are components of the electron transport chain involved in this latter process.

How many intermediates are in the Krebs cycle?

The Krebs cycle (Figure 2) contains 4 and 6 carbon intermediates. Pyruvate (C3) can feed into the Krebs cycle in such a way that the number of C4/C6 intermediates remains the same or increases.

How are fatty acids broken down?

Fatty acids are broken down to acetyl groups (C2) which feed into the Krebs Cycle by addition to a C4 intermediate to produce C6. During the cycle, the added C2 is lost as CO 2 and C4 regenerated. Overall, no increase in the number of molecules of cycle intermediates occurs. Thus, if fatty acids are the sole carbon source, no Krebs cycle intermediates can be removed without shutting it down:

What is the pathway of sugar catabolism?

This is the most common pathway in bacteria for sugar catabolism (It is also found in most animal and plant cells). A series of enzymatic processes result in conversion of sugars into pyruvate, generating ATP (adenosine triphosphate) and NADH (nicotinamide adenine dinucleotide).