Electron transport chain (ETC) is a series of compounds that transfer electrons from electron donor to electron acceptor through redox reactions, and couples the transfer of electrons with proton transfer across the membrane.

The following explanation is from the book "Bioelectrochemistry: Fundamentals, Experimental Techniques and Applications, by P. N. Bartlett"

http://onlinelibrary.wiley.com/book/10.1002/9780470753842

"Bacteria tend to contain redundant electron transport systems. As a result, bacteria can grow under a variety of conditions and can switch between different branches of their electron transport chains depending upon the conditions. Bacteria utilize a range of electron donors in energy generation, together with either oxygen as the ultimate electron acceptor, in aerobic respiration, or other species such as NO3 or SO42, in anaerobic respiration, although in these cases less energy is generated. The electron transport chains in bacteria are very similar to those in the mitochondrion and the principles are the same, although the polypeptide composition of the electron transport proteins in bacteria is usually simpler than those in mitochondria and the proteins involved are located in the cell membrane itself (prokaryotes do not contain separate mitochondria).

Figure 1.15 shows the respiratory chain of marine Vibrio. Notice, in this case, that there are three main complexes, an NADH–quinone reductase, a quinol oxidase, and an NADH–quinone reductase. These are linked together by quinones. In this case, the organism pumps both H+ and Na+ across the membrane to generate both a proton motive force and a transmembrane difference

in the electrochemical potential of Na+. Escherichia coli is able to assemble specific respiratory chains by the synthesis of the necessary dehydrogenase and reductase enzymes in response to the conditions in which it finds itself. As an example, Figure 1.16 shows an electron transport chain for Escherichia coli during anaerobic respiration . In this case, nitrate replaces oxygen as the ultimate electron acceptor."

There is animation that explain ETC both in aerobic and anaerobic conditions:

http://www.sumanasinc.com/webcontent/animations/content/electrontransport.html

Hope this works

Active transport in aerobic bacteria means the required nutrients including ions cross the cell membrane by oxidative process with large amount of energy as ATPs.On other hand,anarobically  carried out by fermentation process with low energy and some solutes pass cell membrane through the difference intra and extra osmotic pressure.

Electron transport chain (ETC) is a series of compounds that transfer electrons from electron donor to electron acceptor through redox reactions, and couples the transfer of electrons with proton transfer across the membrane.

The following explanation is from the book "Bioelectrochemistry: Fundamentals, Experimental Techniques and Applications, by P. N. Bartlett"

http://onlinelibrary.wiley.com/book/10.1002/9780470753842

"Bacteria tend to contain redundant electron transport systems. As a result, bacteria can grow under a variety of conditions and can switch between different branches of their electron transport chains depending upon the conditions. Bacteria utilize a range of electron donors in energy generation, together with either oxygen as the ultimate electron acceptor, in aerobic respiration, or other species such as NO3 or SO42, in anaerobic respiration, although in these cases less energy is generated. The electron transport chains in bacteria are very similar to those in the mitochondrion and the principles are the same, although the polypeptide composition of the electron transport proteins in bacteria is usually simpler than those in mitochondria and the proteins involved are located in the cell membrane itself (prokaryotes do not contain separate mitochondria).

Figure 1.15 shows the respiratory chain of marine Vibrio. Notice, in this case, that there are three main complexes, an NADH–quinone reductase, a quinol oxidase, and an NADH–quinone reductase. These are linked together by quinones. In this case, the organism pumps both H+ and Na+ across the membrane to generate both a proton motive force and a transmembrane difference

in the electrochemical potential of Na+. Escherichia coli is able to assemble specific respiratory chains by the synthesis of the necessary dehydrogenase and reductase enzymes in response to the conditions in which it finds itself. As an example, Figure 1.16 shows an electron transport chain for Escherichia coli during anaerobic respiration . In this case, nitrate replaces oxygen as the ultimate electron acceptor."

There is animation that explain ETC both in aerobic and anaerobic conditions:

http://www.sumanasinc.com/webcontent/animations/content/electrontransport.html

Hope this works

First of all, you need to know that the arrangement of electron carriers in ETC is in order of increasingly more positive E0’(NADH dehydrogenase is the first and cytochromes are the last) and the reduction potential will determine the behavior of a substance which can be either an electron donor or an acceptor.

In aerobic respiration cytochrome c carries the electrons from cytochrome bc1 (Complex III) to cytochrome aa3 (Complex IV). Complex IV in ETC consisting of cytochromes a and a3 is the terminal oxydase in the aerobic bacteria which reduces O2 to H2O. Therefore there is no need of this cytochromes in anaerobic respiration but that doesn’t necessarily mean the lack of this enzymes in all anaerobic bacteria.

But there is a huge variety of electron carriers (especially amongst the cytochromes), it mainly depends on the bacterial species (its enzyme system) and the terminal electron acceptor (or more precisely the reduction potential of the acceptor) which ones are present and used; most facultative bacteria have the full stock of carriers, so they can switch to anaerobic respiration if it’s needed. In my opinion, if you are interested in a certain bacterial species you should look into the chemotaxonomy of it.

The required nutrients including ions cross the cell membrane in aerobic bacteria by oxidative process with large amount of energy as ATPs. In anaerobic bacteria by fermentation process with low energy and some solutes pass cell membrane through the difference intra and extra osmotic pressure.

The answer is very simple and that is the nature of electron acceptor at the end of the chain. 

For aerobic respiration, electrons are finally deposited to O2 through ETC complex IV and generate water, while ATP synthase produces ATP driven by the proton gradient generated by electron transport through complex I to IV.  In the absence of oxygen, one possibility might be that anaerobic bacteria might have different structure of ETC complex IV that can use alternative electron acceptors rather than oxygen to accept electrons. 

What people are saying here is quite valid - but in addition to redundant electron acceptors, e.g. phenazines and nitrates, there are also diverse cytochrome oxidases dedicated to different oxygen regimes within the biofilm - as not all depths of the biofilm colony can access atmospheric oxygen. This is due to the fact that the rate of diffusion of O2 into the biofilm is eventually overcome by the rate of respiration. Depths greater than ~45-60µm are largely anoxic. This is clearly most relevant for biofilms cultured onto solid media and for thick pellicles.  

@William,

It sounds interesting to me that cytochrome oxidases can provide some potential electron acceptors for biofilm bacteria.  But do bacteria really do lot of metabolism in the biofilm? because usually many bacteria are dormant while they are siting in the biofilm matrix.  They will become active until the environment become good for them and when the biofilm is detached and finds a new niche to colonize.

This is not my particular area of expertise, but molecularly you have different terminal electron acceptors, and these may not be fully interchangeable with aerobic terminal oxidases, and so could require dedicated terminal oxidases for different oxygen regimes: aerobic, microaerobic, anoxic. 

Sorry I didn't answer your question:

It isn't that cytochrome oxidases are acting as terminal electron acceptors, its that under varying oxygen regimes you have differing kinetics and affinities for O2 and so have dedicated cytochromes - or rather dedicated orphan catalytic cytochrome subunits, that become unregulated under specific conditions to deal with these stresses, and perhaps to couple terminal transfer to non-aerobic terminal electron acceptors. This may not be true for your system - I'm just suggesting that it is not nearly so simple as having differing terminal electron acceptors in aerobic vs anoxic environments. As I read other posts on this thread - Hahn spells out basically the same thing. And I would not suggest that bacteria embedded in biofilm matrix are always dormant. In our system (what is your system?), we find that matrix becomes unregulated in response to redox stresses (increase in NADH beyond homeostatic levels as result of lack of O2, can be quelled by phenazines or nitrates etc), and that these cells are involved in a slew of signaling pathways and have many functions asides colonization. I do not think much about biofilms in flow environments, but rather study them biochemically and electrochemically grown on solid media. Obviously these conditions are unique and not fully representative of biofilms in nature. 

Aerobic respiration can only occur in the presence of oxygen, while anaerobic respiration doesn't require or utilize oxygen in its energy production. In aerobic respiration, glucose molecules are passed through a chemical reaction chain that produces ATP, carbon dioxide and water and ends with oxygen accepting the free electrons that have been generated. In contrast, anaerobic respiration is cellular respiration that occurs using other molecules as the terminal electron acceptor since oxygen isn't present.

Both aerobic and anaerobic respiration use electron-transport chain-reaction pathways in energy production. However, aerobic respiration produces much more energy, or ATP molecules, than anaerobic respiration. For every molecule of glucose that is metabolized in the presence of oxygen by aerobic respiration, 38 ATP molecules are produced. By contrast, anaerobic respiration produces only two ATP molecules by dividing one glucose molecule into two pyruvic acid molecules in a process known as glycolysis.

Dear Daniel:

I am looking a response for a similar question. The are many possible terminal electron acceptors for respiration. Among them are oxygen, nitrate, fumarate, sulfate , and carbon dioxide or carbonate. These would be converted respectively to water, nitrogen gas, succinate, hydrogen sulfide, and methane. How are the prokaryotes which reduce sulfate or form methane totally different from bacteria such as E.coli and Shewanella which are also capable of anaerobic respiration? In White 2012 Physiology and biochemistry of prokaryotes page 163, the most accurate response that I could found was differences in Ubiquinones (UB)  and  menaquinones (MQ)  (60%, 40% in E.coli growing aerobically) versus anaerobically growing in Nitrate: 0% UQ, 70% demethylmenaquinone (DMQ) and 30% MQ.