The Deepwater horizon oil
spill in 2010 cause catastrophic damage to the marine environment, and will
take many years the previous communities to present again.
78% of the oil spilt was managed to be deleted by natural
means or human intervention by August 2010 the remaining oil most probably
found its way in to the marine sediments. Kimes
et al, aimed to assess which microbial communities were present in the
sediments around the oil spill and determine their metabolic capabilities.
Deep-sea sediment cores were collected between September and
October 2010, from sites close to the DWH site and sites further away to be
used as control groups. The metagenome of each sample was determined, followed
by PCR of function genes including genes coding for; the catalytic subunit of
the anaerobic glycyl radical enzyme (assA
and bssA), alkylsuccinate synthase
and Benzylsuccinate synthases. Finally, phylum level classifications were made
from each metagenome, and differences in the Proteobacteria at the class and
order level, as this group showed great differences between the sites.
This paper presents three new metagenomics data sets from
deep sea sediments following DWH oil spill, when looking at this data along
with previous data sets from the DWH oil spill site there is clear distinctions
in the microbial communities between the sites in the Gulf of Mexico and the ‘control’
site; Peru Margin. Oceanospirillales was previously shown to be a dominant bacterial
order in the deep water oil plume associated with the DWH event (Hazen et al.,
2010). The Kimes et al study did find bacteria in the Oceanospirillales order with many sequences in the meta genome
related to Alcanivorax borkumensis. Over
all there was a similar abundance of Oceanospirillales
sequences found at all 3 sites, and in general a similar abundance of Gammaproteobacteria.
There were higher levels of Deltaproteobacteria in sediment
cores closest to the DWH site, where levels of PAH’s were at their highest.
Clone libraries support of assA and bssA support the metagenomics analysis with
but being found at the site near the DWH and not at the control, unimpacted
site showing the potential for aliphatic and aromatic hydrocarbon degradation.
A main conclusion in this paper is that the lack of
distinctions within the 3 samples maybe caused by a quick degradation of the
oil in the water column, previous papers showed increased levels of oil degrading
bacteria in the water column, and in turn the amount of hydrocarbon loading
that occurred in the deep-sea sediments was not significant enough to promote
microbial growth.
The Authors accept some major downfalls of this study which
may impact on the reliability of the results, including the low replication
number, but it was noted that it was limited due to political and logistical
reasons. A well as this study only revealing a snapshot in time, which may be
at a time when the community was beginning to shift to reflect the increasing importance
of anaerobic microbes. The best way to over-come this is by preforming a time
series study.
I think the strength of this study lies in the interdisciplinary
approach it takes to assess the phylogenetic comparisons and functional
potential of the microbial communities which were effect by the DWH oil spill.
This data as well as previous data suggests that the presence of PAH’s, alkanes
and alkenes may influence the microbial communities which are exposed to
anthropogenic hydrocarbons.
Reviewed paper:
Kimes, N. E., Callaghan, A. V., Aktas, D. F., Smith, W. L., Sunner, J., Golding, B., … Morris, P. J. (2013). Metagenomic analysis and metabolite profiling of deep–sea sediments from the gulf of Mexico following the Deepwater horizon oil spill. Frontiers in Microbiology, 4, . doi:10.3389/fmicb.2013.00050 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3598227/
Hazen, T. C., Dubinsky, E. A., DeSantis, T. Z., Andersen, G. L., Piceno, Y. M., Singh, N., … Mason, O. U. (2010). Deep-sea oil plume enriches indigenous oil-degrading bacteria. Science, 330(6001), 204–208. doi:10.1126/science.1195979 http://science.sciencemag.org/content/330/6001/204
Hi,
ReplyDeleteI was wondering, do the authors suggest what the shift would be like in a few years time? Do they think it will stay Oceanospirillales and Deltaproteobacteria dominated for long periods of time or is it sort of just an inital response, which will then shortly revert back? Also do you think the shift maybe because other organisms that were dominant are killed of by the spill or are the Deltaproteobacteria just more successful under these conditions?
Thank you,
Chloe.
Hi,
ReplyDeleteIn the paper the authors say 'community was just beginning to shift to reflect the increasing importance of anaerobic microbes'- what i took from this is that in a few months/ years there will be an increased domination of the anaerobic bacteria.
I think this shift maybe explained in two ways 1) as you said the oil killed many of the previously dominant microbes, but 2) the Deltaproteobacteria and other related bacteria that can survive and thrive in the presence of the oil are out-competing all the other less tolerant bacteria.
I also think that it is important to note that in the 'control' site there is still similar communities found, this may suggest that the deltaproteobacetia are spreading due to there success, but it may also suggest that in these deep sediments there is already a deltaproteobacetia dominant communitiy, which was then extrapolated due to the oil spill.
I hope this helped answer your questions.
Thank you
Natasha