What are the major groups of bacteria?

Well it depends on what you mean by "group". Bacteria, like all other living things can be grouped into Phylum, Class, Family, Genus, and species. Most commonly scientists refer to the Genus of bacteria like Micrococcus, Staphylococcus, Bacillus, Escherichia... but if you'd like to know groups based on their shape, then there are two main kinds: cocci which are circular, and bacilli which are rod shaped. There are of course other shapes like spiral, curved, stalked...

 

I hope this has helped.

These are not really phylogenetic groups....

Personally I would first broadly sort them in to gram negative and gram positive.

I understand the preference today would be to group them based upon DNA sequences. In that case the following would apply:

 

Thermatogales

Green non-sulphur bacteria

Green sulphur bacteria

Flavobacteria bacteroides

Cyanobacteria

Purple bacteria

Gram positive bacteria

Spirochaetes

 

Slightly more information on each group may be found at this Universe of California Museum of Palaeontology website, or a much more detailed breakdown at the eubacteria page of the Tree of Life. The Tree of Life site is always worth a visit for questions concerning classifcation.

While 16s rRNA has become poppular for higher taxa, they were found to be problematic e.g. at genus or species level. However, even at higher taxa the groups can shift a little. However some are better established than others. The most "official" version, if one wants to call it, is derived from Bergey's manual. Last time I looked there were over 20 phyla (and an enormous group of unclassified ones, so there is potential for more).

Personally I would first broadly sort them in to gram negative and gram positive.

 

 

I agree. I think Gram 'Positive' and Gram 'Negative' are the two major groups that you can divide bacteria into. Then again it also depends on WHAT characteristics of bacteria you want to compare...

Personally I would first broadly sort them in to gram negative and gram positive.

 

This is akin to saying there are two types of Eukaryotes: chlorophyll positive and chlorophyll negative. Although not incorrect, it's a superficial delineation based on a characteristic that's very easy to measure but provides limited biological insight. Same with gram staining, it was once an important method for describing bacteria (couple of decades ago), but has since been replaced with more descriptive measures.

This is akin to saying there are two types of Eukaryotes: chlorophyll positive and chlorophyll negative. Although not incorrect, it's a superficial delineation based on a characteristic that's very easy to measure but provides limited biological insight. Same with gram staining, it was once an important method for describing bacteria (couple of decades ago), but has since been replaced with more descriptive measures.

 

I think that would be sensible first distinction to make! Note: I said FIRST.

I think that would be sensible first distinction to make! Note: I said FIRST.

 

 

It only works if you have a pure culture of bacteria and only about 5% or so of bacterial "species" can be (have been) isolated into cultures. Furthermore, absence/presence of an outer lipopolysaccharide layer is not a monophyletic trait. (Nor is chlorophyl +/- in Euks either for that matter). So while Gram staining is a good tool for instructional microlabs, it's utility in current research science is extremely limited. But of course you can do whatever you want, which is a part of what makes science great.

 

While 16s rRNA has become poppular for higher taxa, they were found to be problematic e.g. at genus or species level. However, even at higher taxa the groups can shift a little. However some are better established than others. The most "official" version, if one wants to call it, is derived from Bergey's manual. Last time I looked there were over 20 phyla (and an enormous group of unclassified ones, so there is potential for more).

 

As of 2007 we are up to 30 phyla with cultured representatives and 70 phyla defined solely by culture independent techniques for Bacteria. (Based on 16s rRNA sequence space.) Using metagenomics and metaproteomics (among other techniques, like good old fashion culturing) we are just beginning to scratch the surface of the accompanying phenotypic/metabolic diversity. It's both an overwhelming and exciting time to be a microbiologist.

Edited September 11, 201015 yr by Rip:20

Well. coming from the "omics" side I have to add that right now we need to start making sense of the data rather than piling up on it. A serious is issue that many coming into the omic field try to do is non-hyptothesis driven proteomics or transcriptomics analyses (I admit that a decade or so back I did the very same). When I give talk how to use the omics toolbox I usually make an opening statement like "don't get too excited, if you want answers".

Rather unfortunately many PIs see the methodologies little more than a paper making stint. Anyway, just needed to rant a bit.