Intestinal microbiota composition in fishes is influenced by host ecology and environment:

 

Alongside our current lecture series’ it is well known that the digestive tract of vertebrates are comprised by complex assemblages of micro-organisms. This is the gut microbiota, although all vertebrates harbour this microbiota of the gut most of the current information on the composition of this microbiota is derived from mammals. This microbiota has been shown to be related to the host’s diet, anatomy and phylogeny. Unfortunately mammals only constitute fewer than ten percent of all vertebrate species and so it remains to be seen whether this trend spreads into more diverse and ancient vertebrate lineages.

 

The authors conducted a detailed meta-analysis of 25 bacterial 16S rRNA gene sequence libraries derived from the intestines of different fish species. They then compared this to a large already known collection of rRNA gene sequence data sets for a range of free living and host-associated bacterial communities.

 

The results demonstrated that salinity is a major characteristic in the intestinal microbiota structure, as during this study the authors compared freshwater, saltwater and estuarine fish and saw that the microbiota formed significantly different clusters, which was consistent with a previous study (Roeselers et al, 2011) and thus increases the validity of these conclusions as they have been reciprocated. They found that for each type of fish these differences were due to an increased representation of OTU’s from the order; Aeromonadales within freshwater fish and Vibrionales in saltwater fishes.

 

However there is a distinct lack of research regarding this and so more research needs to be done to see which aspect of salinity alters these niches for the OTU’s. Whether it is the microbes within the water altering with this salinity or whether the changes are within the hosts themselves.

 

The authors also noted that the prey type alters the composition and this follows on from the lectures that Dan has been giving us as he has already mentioned this. There isn’t a distinct divide between these trophic levels as there is overlap. What was noted was that omnivorous fish all clustered near the free-living and invertebrate-associated communities, carnivorous fish generally clustered with carnivorous mammals, and three of the four herbivorous fish communities were similar to mammalian communities.

 

Overall the author’s conclusions state that; their results suggest that variation in gut microbiota composition in fishes is strongly correlated with species habitat salinity, trophic level and possibly taxonomy. These are only a few aspects that have been tested and so in the future more possible factors need to be tested such as; water depth and temperature etc.

 

This study is very interesting and like a number of papers that I have reviewed is only a new development and so is one to keep an eye out for in the future.

 

The paper can be found at:

http://onlinelibrary.wiley.com/doi/10.1111/j.1365-294X.2012.05646.x/pdf

 

Reference

 

Wong, S and Rawls, J. (2012). Intestinal microbiota composition in fishes is influenced by host ecology and environment. Molecular Ecology, Volume 21, 3100-3102.