Distinct, ecotype-specific genome and proteome signatures in the marine cyanobacteria Prochlorococcus

• Type of Material: Article
• Authors: Sandip Paul, Indian Institute of Chemical Biology; Anirban Dutta, Indian Institute of Chemical Biology; Sumit K. Bag, Indian Institute of Chemical Biology; Sabyasachi Das, Emory University; Chitra Dutta, Indian Institute of Chemical Biology
• Language: English
• Date: 2010
• Publisher: BioMed Central
• Publication Version: Final Published Version
• Copyright Statement: ©2010 Paul et al; licensee BioMed Central Ltd.
• License: Creative Commons Attribution 2.0 Generic
• Final Published Version (URL): http://www.biomedcentral.com/1471-2164/11/103
• Title of Journal or Parent Work: BMC Genomics
• ISSN: 1471-2164
• Volume: 11
• Start Page: 103
• End Page: 103
• Grant/Funding Information: This work was supported by the Department of Biotechnology, Government of India (Grant Number BT/BI/04/055-2001) and Council of Scientific and Industrial Research (Project no. CMM 0017).; SP and AD are supported by Senior Research Fellowships from Council of Scientific and Industrial Research, India.
• Research Categories: Biology, Bioinformatics; Health Sciences, Pathology; Engineering, Chemical

Abstract

Background The marine cyanobacterium Prochlorococcus marinus, having multiple ecotypes of distinct genotypic/phenotypic traits and being the first documented example of genome shrinkage in free-living organisms, offers an ideal system for studying niche-driven molecular micro-diversity in closely related microbes. The present study, through an extensive comparative analysis of various genomic/proteomic features of 6 high light (HL) and 6 low light (LL) adapted strains, makes an attempt to identify molecular determinants associated with their vertical niche partitioning. Results Pronounced strand-specific asymmetry in synonymous codon usage is observed exclusively in LL strains. Distinct dinucleotide abundance profiles are exhibited by 2 LL strains with larger genomes and G+C-content ≈ 50% (group LLa), 4 LL strains having reduced genomes and G+C-content ≈ 35-37% (group LLb), and 6 HL strains. Taking into account the emergence of LLa, LLb and HL strains (based on 16S rRNA phylogeny), a gradual increase in average aromaticity, pI values and beta- & coil-forming propensities and a decrease in mean hydrophobicity, instability indices and helix-forming propensities of core proteins are observed. Greater variations in orthologous gene repertoire are found between LLa and LLb strains, while higher number of positively selected genes exist between LL and HL strains. Conclusion Strains of different Prochlorococcus groups are characterized by distinct compositional, physicochemical and structural traits that are not mere remnants of a continuous genetic drift, but are potential outcomes of a grand scheme of niche-oriented stepwise diversification, that might have driven them chronologically towards greater stability/fidelity and invoked upon them a special ability to inhabit diverse oceanic environments.