With the ever present threat of global warming happening as we speak (and an expectation that ocean temperatures will increase by a few degrees during this century) it is of interest to everyone in the biological community as to what the effect of this climate change will have on organisms from the largest mammals to the smallest microbes. This study looked at microbes, the vibrio genus to be specific, the reason this is significant is due to the fact that most of todays diseases and illnesses are down to bacteria and prokaryotes so it will be interesting to see what is going to happen with them in this current climate, will illnesses due to vibrio's increase or decrease?
There is some published material regarding the effect that long term warming of the oceans has on eukaryotic organisms, but there is nothing looking at prokaryotes and the effect on their diversity and abundance, the possible reasons for this are due to the fact that in many peoples eyes prokaryotes due to the fact they belong to a lower trophic level are less sensitive to environmental change and therefore arent studied as much.
Vezzulli et al (2012) performed the first published study looking at prokaryotes and their reaction to this ocean temperature increase, the study lasted 44 years, from 1961 to 2005, during this time using a CPR (continuous plankton recorder) 55 samples were collected from 2 areas located off the Rhine & Humber estuaries in the North Sea, the outer limit of these sites being within 50 nautical miles from the North Sea coast. The way the recorder works is by collecting phyto and zooplankton and any other prokaryotes that get caught in its 270 micrometre mesh which collects everything from seven metres and above (so collects from the surface layer as the recorder is dragged behind any commercial waterborne vessel), these collections then can be analysed in numerous ways back in laboratories. One type of analysis that was done was the PCR and then pyrosequencing which gave the genomes and overall identity of the prokaryotes collected. All of the collections were done in August of the years they were collected.
The results from this study showed that with this increase in sea temperature during the last half century, there has also been a dramatic increase in the abundance of Vibrio bacteria. This includes the well known and studied Vibrio Cholerae. With this increase in abundance there was also a noticeable increase in dominance of the whole genus. This observed increase in temperature explained 45% of the vibrio's variance, with environmental variables explaining the rest. With this increase in abundance there was also a noted increase in diseases related to bathing in these waters. So it was concluded that with this increase in temperature there is an increase in the vibrio genus and their diseases.
I reviewed this article because it is one of a kind, as there is barely any information on prokaryotic alterations in recent years and it will hopefully provide a back bone for this type of study and eventually cause more studies to be done in the future.
Source:
Luigi Vezzulli et al. (2012) - Long Term Effects of ocean warming on the prokaryotic community: evidence from the vibrios.
I think it’s important to clarify a few points and say why the vibrios are such an important group and why it was possible to study them by retrospectively examining silk samples from the CPR collected over 44 years. The CPR silk primarily traps zooplankton and larger phytoplankton. Vibrios are known to associate with the exoskeleton of zooplankton such as copepods via attachment to chitin. Because they are copiotrophic bacteria, they will aggregate on particles of detritus containing chitin and other nutrients. All the samples analysed came from CPR transects in the late summer – when abundance of vibrios would be expected to be at its highest. This is of particular relevance in the North Sea, because there is evidence of human infections associated with bathing during recent hot summers (see Baker-Austin et al (2012) www.nature.com/nclimate/journal/vaop/ncurrent/fig_tab/nclimate1628_ft.html). To clarify the methodology, it’s important to note that the authors used Q-PCR of (real-time PCR) with primers that amplify 16SrRNA from vibrios - this is how they were able to estimate relative abundance. Of course, the CPR was thought of long before the advent of molecular techniques and it took a lot of work by scientists at SAHFOS here in Plymouth to develop methods for recovering good quality DNA from archived samples stretching back over many years. This has also been used to study changes in communities of E. huxleyi and its viruses (e.g. see Ripley et al. 2008, www.ncbi.nlm.nih.gov/pubmed/18358549
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