Bacterioplankton diversity in the estuarine regions of two peninsular rivers: A metagenomic approach

Abstract

ObjectiveIn this present study we evaluated the bacterioplankton diversity employing a culture independent high throughput 16srRNA pyro-sequencing technique in two selected estuarine regions that belongs to two peninsular rivers on which the people living in the area heavily depend for their water needs. In spite of several advantages to metagenome based bacterioplankton diversity analysis, no such studies have been carried out in the region so far. MethodsSamples were collected from three different sites for each estuaries. A comparative study on physico-chemical analysis was done on water samples from the estuaries using standard analytical methods. High-throughput sequencing reads obtained from metagenomic sequencing were classified into a taxonomic category using the NCBI taxonomy reference database. ResultIn the study we observed higher percentage composition of bacterioplanktons appertaining to the actinobacteria, cyanobacteria, and proteobacteria groups which can be attributed to higher levels of water nutrients such as nitrates, nitrites and phosphates. Firmicutes identified in the samples indicates the faecal contamination in the water. Apart from these numerous nitrogen-metabolizing bacteria, such as Roseobacter, Nitratiruptor, and Sulfitobacter, were present, as observed. One of the most common bacterioplankton species that is responsible for the breakdown of different types of organic matter is the Roseobacter. Similarly, nitratiruptor is a type of bacteria that reduces nitrite and can break down nitrate in water. Sulfitobacter and Pseudoruegeria are other two strains observed in both the Chaliyam and Dharmadam estuarine regions. It is reported that the Sulfitobacter strains are predominantly distributed in the areas of oil polluted marine environments;it has been associated with hydrocarbon removal from seawater. ConclusionMost of the diverse bacterioplanktons reported are capable of utilizing the dissolved organic matter for their growth and functioning. Isolation of such bacterial communities is having great significance in the aspects of waste water treatment and pollution abatement. We did not observe any major difference in diversity of particle associated bacterioplanktons in the two estuaries investigated. However, there was a significant variation observed in the diversity of free living bacterioplankton attributed to changes in physio-chemical parameters. Overall, metagenomics is a more effective and insightful way to examine microbial populations than standard culture techniques.