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Gemmatimonadetes
By: Mark De Jesus
Institution: Pace University
Feb 2013
Gemmatimonadetes is a new phylum, whose first cultivable member was discovered in 2003,
Gemmatimonas Aurantiaca, which the phylum is also named after. The name is derived from Latin
gemmatus meaning “provided with buds” and Monas meaning “one unit”, thus the name
Gemmatimonas, a budding unit. They found this specific bacterium in sewage treatment plants,
specifically in the activated sewage, a process where they treat the sewage with air (mainly Oxygen) and
a plethora of other bacteria and protozoa. Although others of this family have been seen through
genetic clones, by using 16S rDNA sequencing, G. Aurantiaca was the only one they were able to grow in
a lab. This then brings us to Gemmatimonadetes 4 subdivisions, and see how far reaching this Bacteria
really is.
Using DNA cloning and referencing with G. Aurantiaca, scientists were able to see that this
phylum is quiet prevalent in nature by getting. Scientists were able to find DNA matches of
Gemmatimonadetes in terrestrial soil samples such as arid soils, and like G. Aurantiaca, sludge. What is
rather surprising though is that they were also able to clone DNA from deep sea soil samples, gas
hydrates, and Antarctic marine sediment. Seeing this spread, scientists split the phylum into 4
subdivisions, each subdivision being a little different from one another due to habitat. G. Aurantiaca
belongs in subdivision one, since it is found in a terrestrial habitat, and almost genetically identical to
others of the phylum that are terrestrial. Type 2 and 4 on the other hand are closer genetically than the
terrestrial subdivision, these 2 are found in aquatic habitats. They even share a common symbiote, the
sponge, but they differ since subdivision 2 is found in the deep sea, while types 4 are found in salt
marshes. The 4th division is unique in its own right since it has a mix of both subdivision 1 and
subdivision 2, hence why it is rare and only 2 full genetic strands have been cloned, one from forest soil,
and the other in a gas hydrate. So as we can see we have an interesting bacterium, with diverse habitats
that DNA clones can be found.
Gemmatimonas Aurantiaca is the first bacteria from this phylum that scientists are able to
isolate and culture for this phylum. G. Aurantiaca is a rod shaped, gram negative bacteria; it also has an
orange to pink tint, and is motile. What’s weird about them though is seen in reproduction, sometimes
its binary fission, but other times look more like budding, due to the unequal size of the new cell. The
optimal temperature G. Aurantiaca grows best at is approximately 30o C and is an aerobic heterotroph,
but strains have been found in anaerobic-aerobic batches, which were quiet surprising to scientists.
Carbon is acquired solely from very specific compounds, yeast extract, polypepton, succinate, acetate,
gelatin, and benzoate, which is why scientists suspect it has been hard to culture these microorganisms
in the lab. Along with being fastidious bacteria, it has a minimum double rate of 12 hours in NM-1 media
broth, which compared to E. Coli’s 2 hours, is a lifetime. What scientists did to isolate this strain of
Gemmatimonadetes, took almost 3 weeks just to get a pinpoint size colony. In NM-1 media agar they
streaked and isolated this bacterium, until they were sure it was pure form. They then streaked again
with the same media, with a temp of 250-350C, a ph of 6.5-9.5 aerobically, which they then incubated for
two weeks. They discovered that the optimal growth factors for G. Aurantiaca required a pH of 7.0, and
a temp of 300C, to create that pinpoint size colony. It is no wonder this phylum has had no cultivated
representative, it is slow growing, very picky, not only environment wise, but also food wise.
Zhang et al proposed that this phylum be made novel. What this means is that it stands out
from other bacteria. What makes Gemmatimonadetes so special you might ask? Well an interesting
fact of G. Aurantiaca is that it lacks DAP (diaminopimelic acid) which is more common in Gramm positive
bacteria, which is fine and some other Gramm negative bacteria do have this trait as well, so it’s not
because of this. The reason is that it has an atypically wide gap in its periplasmic space, for a Gramm
Negative Bacteria, and the second reason they propose this bacteria phylum to be novel is that fact that
it has fatty acids that are not found in this type of bacteria.
With being novel bacteria what might you ask do these bacteria do? Well through observing G.
Aurantiaca scientists believe that they accumulate polyphosphates. What this means is that they
facilitate the removal of Phosphorous in the environment. This explains why G. Aurantiaca was found in
the active water, it is sewage being treated, and sewage has an enormous amount of Phosphorous in it.
Hence its relevancy to humans, it helps clean our sewage, among other microbes found in water
treatment.
G. Aurantiaca, the model of the Gemmatimonadetes. Though scientists don’t believe that all
species of the new phylum facilitate the same niche as G. Aurantiaca, they are sure that the cell envelop
should be the same for the rest of the phylum, but since it has been the only Bacterium grown from the
phylum, it is deemed appropriate for now.
References:
Gemmatimonas aurantiaca gen. nov., sp. nov., a Gram-negative, aerobic, polyphosphateaccumulating micro-organism, the first cultured representative of the new bacterial phylum
Gemmatimonadetes phyl. nov.
Int J Syst Evol Microbiol 2003 53: 1155-1163