Bacterial dispersal is an interesting topic within the marine environment, showing complex biogeographical patterns. Because there are so many different factors which govern any individual microbes’ distribution (ie, flagellum/cilia, seasonal currents/upwellings etc.) this paper focuses on passive dispersal (abiotic factors) by measuring the abundance of Desulftomaculum (thermophillic endospores) found within permanently cold marine sediments. As they do not actively move or reproduce in the endospore state, the number found within each layer of the sediment can be attributed to abiotic factors.
This study has been done before at a different location and three phylotypes genetically identified in the current study were found in the previous one. In total there were 23 phylotypes identified, 19 of which were novel. The endospores decreased exponentially in abundance as you go down through the sediment; 104 cells per cm3 at the surface, down to 1 cell per cm3 6.5 metres down. This provided a half-life between 150 and 440 years for the sulphate reducing thermophillic endospores. It also shows a remarkable flow of endospores which circulates in the water column, 104 per cm3 in an environment which does not promote growth! This could be due to anthropomorphic causes, oil pumps in the surrounding area being an unnatural source of SRB but no tests were done to identify this.
The Authors identified two optimum temperatures for sulphate reduction by Desulftomaculum and showed a 10 fold difference in sulphate reduction when different samples were cultured with an amendment of organic substrates. This amendment also increased the numbers of limited populations found within their samples. This, although just methodology, could optimise further work into sulphate reducers.
This method although giving interesting insights into the thermophiles half-life has limitations unless we know either their origin or abundance at the origin. However because 3 phylotypes were isolated from two distinct sites, one in a previous study, it is hypothesized those bacteria originate from a common warm anoxic environment.
Hi Myles,
ReplyDeleteNice post, it is interesting to think that thermophiles are not just found at thermal vents. Do you think there are any significant uses (medical or industrial) or research advantages of finding these novel phylotypes? What do you think the next step in the research is?
Also I am slightly confused by your comment "oil pumps in the surrounding area being an unnatural source of SRB", how exactly would oil pumps provide a source of energy?
Thanks, Harri
Hey Harri,
ReplyDeleteThe thermophiles are found away from vents, but they are endosporylated so in suspension as it were. Im not sure of the biological impact of the new phylotypes, presumably it is just useful in a scientific context.
The Oil Pumps have tubes going into the sediment, and energy (heat) is given off either at the surface or on the pipes themselves, thus allowing these bacteria to grow in these conditions, and as it is human influence, its not a natural source of the endosporylated bacteria :)
hope this helps! Myles
The idea that hydrothermal vents are spewing out bacteria that are raining down on the sediments thousands of miles away prompts us to reconsider the old adage about global microbial distribution - "everything is everywhere, but the environment selects". There is a nice short commentary by Patterson (2010) about an earlier paper from this group here http://www.sciencemag.org/content/325/5947/1506.short
ReplyDelete[Science full text is only available on campus].