Ecology of Vibrio species and bacterial communities across an estuarine continuum in the Bay of Bengal

GÄRDES, A. ; RASHID, H. ; LARA, R. J.; NEOGI, S. B.; KOCH, B. P.; KOPPRIO, G. A.

Leipzig

Simposio; ISME 17 17th International Symposium on Microbial Ecology; 2018

International Society of Microbial Ecology

Culturable and non-culturable Vibrio and bacterial communities and their relation with water quality, nutrients and isotopic markers were studied through a salinity and pollution gradient in the Karnaphuli estuary (Bangladesh) during pre- and post-monsoon seasons. Canonical Correspondence Analysis and Spearman Rank correlations revealed the strong influence of salinity and organic nutrients on the distribution of culturable Vibrio counts, copies of outer membrane protein gene (ompW) for Vibrio cholerae determined by qPCR and cells counts based on CARD-FISH probes for Vibrio spp. The relative abundance of the order Vibrionales after 16S rRNA analyses followed the same trend. A pattern between the abundance of the cholerae toxin gene (ctxA) and water quality or biogeochemical factors was not clearly observed. The important role of bentho-pelagic processes and particulate organic matter in the dynamic of Vibrio was inferred. The enrichment in the δ13C signature of the particulate organic matter (POM) at the marine stations coincided with a higher abundance of Oceanospirillales, Rhodobacterales and Vibrionales. Organisms of these orders may degrade estuarine organic matter enriching the δ13C pool. The depletion of the δ15N signature coincided with the maximum of ammonium, coliforms, dissolved organic nitrogen and the relative abundance of Arcobacter spp. at the sewage discharge station in the Post-monsoon season. This phenomenon evidenced the importance of this genus in the nitrogen cycle and ammonification of organic compounds. Global change is likely to increase the trophic state and salinisation of estuaries, and consequently, it may impact on the dynamic of Vibrio, bacteria and human coastal communities.