2. Metabolismo Reproducción (crecimiento) Diferenciación Comunicación Movimiento Evolución Características de la vida celular
3. Crecimiento Microbiano : Cambio en el número de células por una unidad de tiempo determinada. Tiempo de generación (duplicación): Tiempo requerido para que una célula se divida en dos. El tiempo puede ser minutos, hora o días.
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31. TIPOS DE FERMENTACIÓN: Fermentación alcohólica, producida principalmente por levaduras, as bacterias lo producen por otras vías. Fermentación hómoláctica. Se fermenta la glucosa hasta ácido láctico por la reducción de piruvato mediante la acción de la enzima lactato deshidrogenasa. Streptococcus , Pediococcus , Lactobacillus . Fermentación heteroláctica. Se fermenta la glucosa produciendo CO 2 , ácido fórmico, ácido acético entre otros. Fermentación del ácido propiónico. Se produce este compuesto por la acción de bacterias anaerobias como Propionibacterium . Fermentación ácido mixta. Se produce aparte de ácido láctico, ácido acético, succínico y fórmico. Es llevada a cabo por la mayoría de las enterobacterias, E. coli , Shigella y Salmonella . Fermentación de butanodiol. Se produce por la acción de Serratia , Enterobacter y Bacillus . Fermentación del ácido butírico. Se produce por Clostridium .
Notas del editor
Figure: 06-01 Caption: The general process of binary fission in a rod-shaped prokaryote. For simplicity, the nucleoid is depicted as a single circle in green.
Figure: 05-24 Caption: Scheme of anabolism and catabolism showing the key role of ATP and the proton motive force in integrating the processes. Monomers can come preformed as nutrients from the environment or from catabolic pathways like glycolysis and the citric acid cycle.
Figure: 12-005 Caption: Blooms of purple sulfur bacteria. (a) Thiopedia roseopersicinia , in a sulfide spring in Madison, Wisconsin. The bacteria grow near the bottom of the spring pool and float to the top (by virtue of their gas vesicles) when disturbed. The green color is from cells of the eukaryotic alga Spirogyra .
Figure: 05-23a Caption: Energetics and carbon flow in (a) chemoorganotrophic respiratory metabolism. Note the importance of electron transport leading to proton motive force formation.
Figure: 05-23b Caption: Energetics and carbon flow in (b) chemolithotrophic metabolism. Note the importance of electron transport leading to proton motive force formation.
Figure: 05-23c Caption: Energetics and carbon flow in (c) phototrophic metabolism. Note how in phototrophic metabolism carbon for biosynthesis can come from CO 2 (photoautotrophy) or organic compounds (photoheterotrophy). Note also the importance of electron transport leading to proton motive force formation.
Figure: 05-08 Caption: Example of an oxidation–reduction reaction: The formation of H 2 O from the electron donor H 2 and the electron acceptor O 2 .
Figure: 05-09 Caption: The electron tower. Redox couples are arranged from the strongest reductants (negative reduction potential) at the top to the strongest oxidants (positive reduction potentials) at the bottom. As electrons are donated from the top of the tower, they can be “caught” by acceptors at various levels. The farther the electrons fall before they are caught, the greater the difference in reduction potential between electron donor and electron acceptor and the more energy that is released. As an example of this, on the left is shown the differences in energy released when a single electron donor, H 2 , reacts with any of three different electron acceptors, fumarate, nitrate, and oxygen.
Figure: 05-13a-b Caption: Energy conservation in fermentation and respiration. (a) In fermentation, ATP synthesis occurs as a result of substrate-level phosphorylation; a phosphate group gets added to some intermediate in the biochemical pathway where it becomes a “high-energy” phosphate group and eventually gets transferred to ADP to form ATP. (b) In respiration, the cytoplasmic membrane, energized by the proton motive force, dissipates some of that energy in the formation of ATP from ADP and inorganic phosphate (Pi) in the process called oxidative phosphorylation. The coupling of the proton motive force to ATP synthesis occurs by way of a membrane protein enzyme complex called ATP synthase (ATPase) (see Section 5.12 and Figure 5.21).
Figure: 05-19 Caption: Electron transport chains and their relation to E 0 ' . Shown here is one example of an electron transport system, leading to the transfer of electrons from substrate to O 2 . This particular sequence is typical of the electron transport chain of the mitochondrion of eukaryotic cells and that of some Bacteria (for example, Paracoccus denitrificans ). The electron transport chain in Escherichi a coli lacks cytochromes c and aa 3 , and instead electrons go directly from cytochrome b to cytochrome o or d (the latter has a similar E 0 ' to cytochrome aa 3 ), which is the terminal oxidase (Figure 17.37). By breaking up the complete oxidation into a series of discrete steps, energy conservation is possible through proton motive force formation leading to ATP synthesis. Compare color-coding here with those in Figure 5.9.
Figure: 12-017 Caption: Typical pseudomonad colony and cell morphology and a biochemical pathway common in pseudomonads. (c) The Entner–Doudoroff pathway, the major means of glucose catabolism in pseudomonads.
Figure: 05-22a Caption: The citric acid cycle (CAC). (a)The CAC begins when the two-carbon compound acetyl-CoA (formed from pyruvate) condenses with the four-carbon compound oxalacetate to form the six-carbon compound citrate. Through a series of oxidations and transformations, this six-carbon compound is ultimately converted back to the four-carbon compound oxalacetate, which then begins another cycle with addition of the next molecule of acetyl-CoA.
Figure: 05-20 Caption: Generation of the proton motive force during aerobic respiration. The figure shows the orientation of key electron carriers in the membrane of an organism like Paracoccus denitrificans , a model prokaryote for studies of respiration. The + and – charges across the membrane represent H + and OH - , respectively. Abbreviations are as follows: FMN, flavoprotein; Q, quinone; Fe/S, iron sulfur protein; cyt a, b, c, cytochromes (b L and b H , low and high potential b-type cytochromes, respectively). At the quinone site a recycling of electrons occurs during the “Q cycle.” This is because electrons from QH 2 can be split in the bc1 complex (Complex III) between the Fe/S protein and the b-type cytochromes. Electrons that travel through the latter reduce Q (in two, one-electron steps) back to QH 2 , thus increasing the number of protons pumped at the Q-bc 1 site. Electrons that travel to Fe/S proceed to reduce cytochrome c1 and then cytochrome c, and then a-type cytochromes in Complex IV, eventually reducing O 2 to H 2 O (two hydrogen atoms are required to reduce For simplicity, protein Complex II, the succinate dehydrogenase complex, is not shown in this scheme. The numbers of the complexes shown are those used by convention by scientists in the field of membrane bioenergetics. Compare this electron transport chain with that of Escherichia coli , shown in Figure 17.37.
Figure: 05-21 Caption: Structure and function of ATP synthase (ATPase). F 1 consists of five different polypeptides present as an 3 3 complex. F 1 is the catalytic complex responsible for the interconversion of ADP + P i and ATP. F 0 is integrated in the membrane and consists of three polypeptides in an ab 2 c 12 complex. Subunit a is responsible for channeling protons across the membrane while subunit b protrudes outside the membrane and forms, along with the b 2 and subunits, the stator. As protons enter, the dissipation of the proton motive force drives ATP synthesis. The ATPase is reversible in its action; that is, ATP hydrolysis can drive formation of a proton motive force.
Figure: 12-009 Caption: Reactions involved in the oxidation of inorganic nitrogen compounds by chemolithotrophic nitrifying bacteria (also Figures 17.32 and 17.33).
