Phylogenetic comparisons of a coastal bacterioplankton community with its counterparts in open ocean and freshwater systems

In order to extend previous comparisons between coastal marine bacterioplan kton communities and their open ocean and freshwater counterparts, here we summarize and provide new data on a clone library of 105 SSU rRNA genes rec overed from seawater collected over the western continental shelf of the US A in the Pacific Ocean. Comparisons to previously published data revealed t hat this coastal bacterioplankton clone library was dominated by SSU rRNA g ene phylotypes originally described from surface waters of the open ocean, but also revealed unique SSU rRNA gene lineages of beta Proteobacteria rela ted to those found in clone libraries from freshwater habitats. beta Proteo bacteria lineages common to coastal and freshwater samples included members of a clade of obligately methylotrophic bacteria, SSU rRNA genes affiliate d with Xylophilus ampelinus, and a clade related to the genus Duganella. Ln addition, SSU rRNA genes were recovered from such previously recognized ma rine bacterioplankton SSU rRNA gene clone clusters as the SAR86, SAR11, and SAR116 clusters within the class Proteobacteria, the Roseobacter clade of the alpha subclass of the Proteobacteria, the marine group A/SAR406 cluster , and the marine Actinobacteria clade. Overall, these results support and e xtend previous observations concerning the global distribution of several m arine planktonic prokaryote SSU rRNA gene phylotypes, but also show that co astal bacterioplankton communities contain SSU rRNA gene lineages (and pres umably bacterioplankton) shown previously to be prevalent in freshwater hab itats. (C) 2000 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.