Vibrio and Bacterial Communities Across a Pollution Gradient in the Bay of Bengal: Unraveling Their Biogeochemical Drivers

KOPPRIO, GERMÁN A.; NEOGI, SUCHARIT B.; RASHID, HARUNUR; ALONSO, CECILIA; YAMASAKI, SHINJI; KOCH, BORIS P.; GÄRDES, ASTRID; LARA, RUBÉN J.

Frontiers in Microbiology

Open Access

Lugar: Hong Kong; Año: 2020 vol. 11 p. 1 - 16

The highly populated coasts of the Bay of Bengal are particularly vulnerable towater-borne diseases, pollution and climatic extremes. The environmental factorsbehind bacterial community composition and Vibrio distribution were investigated inan estuarine system of a cholera-endemic region in the coastline of Bangladesh.Higher temperatures and sewage pollution were important drivers of the abundance oftoxigenic Vibrio cholerae. A closer relation between non-culturable Vibrio and particulateorganic matter (POM) was inferred during the post-monsoon. The distribution ofoperational taxonomic units (OTUs) of Vibrio genus was likely driven by salinity andtemperature. The resuspension of sediments increased Vibrio abundance and organicnutrient concentrations. The d13C dynamic in POM followed an increasing gradient fromfreshwater to marine stations; nevertheless, it was not a marker of sewage pollution.Bacteroidales and culturable coliforms were reliable indicators of untreated wastewaterduring pre and post-monsoon seasons. The presumptive incorporation of depleted ammonium derived from ammonification processes under the hypoxic conditions, bysome microorganisms such as Cloacibacterium and particularly by Arcobacter nearbythe sewage discharge, contributed to the drastic d15N depletion in the POM. The likelycapacity of extracellular polymeric substances production of these taxa may facilitate thecolonization of POM from anthropogenic origin and may signify important properties forwastewater bioremediation. Genera of potential pathogens other than Vibrio associatedwith sewage pollution were Acinetobacter, Aeromonas, Arcobacter, and Bergeyella.The changing environmental conditions of the estuary favored the abundance of earlycolonizers and the island biogeography theory explained the distribution of somebacterial groups. This multidisciplinary study evidenced clearly the eutrophic conditionsof the Karnaphuli estuary and assessed comprehensively its current bacterial baselineand potential risks. The prevailing conditions together with human overpopulationand frequent natural disasters, transform the region in one of the most vulnerableto climate change. Adaptive management strategies are urgently needed to enhanceecosystem health.