In situ Activity of NAC11-7 roseobacters in Coastal Waters off the Chesapeake Bay based on ftsZ Expression

Abstract

Phylogenetic analysis of sequences of the cell division gene ftsZ retrieved from the Atlantic coast revealed an interesting subgroup NAC11-7, which was targeted by a specifically designed and optimized Taqman assay in diel samples collected in situ and in parallel on-deck incubations. Rapid changes of ftsZ gene copies and the patchy distribution of other phylotypes at different time points suggested that different NAC11-7 populations were sampled. Strong correlations between ftsZ expression and gene abundance (r-squared=0.62), and between ftsZ expression and water temperature (r-squared=0.73) for in situ samples suggested non-synchronous growth of NAC11-7 group. Contrastingly, a sharp 9:00 AM peak of ftsZ expression in the on deck incubation experiment suggested synchronous growth. We propose a possible mixed model in which a certain fraction of the population is synchronously dividing, while a background of asynchronously dividing NAC11-7 cells also exist, some of which are expressing ftsZ at any given time.