Characterization of psychrotrophic bacteria in the surface and deep-sea waters from the northwestern Pacific Ocean based on 16S ribosomal DNA analysis

Seventy-eight 4 degrees C-culturable bacteria were isolated using ZoBell 2216E medium from surface (0-200 m) and deep-sea (1000-9671 m) waters in the northwestern Pacific Ocean. Growth studies indicated that all 4 degrees C-culturable bacteria were psychrotrophs. Six phylotypes were observed in the surface water samples and 8 phylotypes in the deep-sea waters. Phylogenetic characterization based on 16S ribosomal DNA sequence analysis of the representative phylotypes revealed that some bacterial genera, Pseudoalteromonas, Photobacterium, and Vibrio, were common to surface and deep-sea waters, and others, Pseudomonas and Halomonas, specifically occurred in surface water. Overall, the members of Vibrionaceae appear to be dominant in both habitats.