The taxonomic significance of the growth response to Na+by strains ofVibrio

Abstract

Eighty regional Vibrio strains were studied for their growth responses at 13 Na+concentrations. Using a chemically defined plating medium, together with a multipoint inoculation technique, approximately 45% of the strains showed a specific growth requirement for Na+. The remaining strains grew, with a lag period, on the basal medium that contained about 2 mM background Na+. Based on the growth responses to Na+, a numerical analysis was used to explore differences between the strains. A dendrogram was produced in which the strains were grouped into four major clusters. At an equivalent level of similarity the cluster composition was not significantly different from that shown in a second dendrogram that was based on standard tests recommended in the 9th edition of Bergey's Manual of Determinative Bacteriology. The study showed that, over a range of concentrations, the growth response to Na+was taxonomically significant for Vibrio strains.Key words: Vibrio, marine bacteria, Na+requirement, growth response.