engleski

Lineage-specific growth curves document large differences in response of individual groups of marine bacteria to the top-down and bottom-up controls

Marine bacterioplankton represent a diverse assembly of species differing largely in their abundance, physiology, metabolic activity and role in the microbial food webs. To analyse their sensitivity to bottom-up and top-down controls, we performed a manipulation experiment where grazers were removed, with or without the addition of phosphate. Using amplicon-reads normalization by internal standard (ARNIS) we reconstructed growth curves for almost 300 individual phylotypes. Grazer removal caused a rapid growth of most bacterial groups, which grew at rates 0.6 - 3.5 day-1, with the highest rates (>4 day-1) recorded among Rhodobacteraceae, Oceanospirillales, Alteromonadaceae and Arcobacteraceae. Based on their growth, response the phylotypes were divided into three basic groups. Most of the phylotypes responded positively to both grazer removal as well as phosphate addition. The second group (containing e.g. Rhodobacterales and Rhizobiales) responded to the grazer removal, but not to the phosphate addition. Finally, some clades such as SAR11 and Flavobacteriaceae responded only to phosphate amendment, but not to grazer removal. Our results show large differences in bacterial responses to experimental manipulations at the phylotype level and document different life strategies of marine bacterioplankton. In addition, growth curves of 130 phylogroups of aerobic anoxygenic phototrophs were reconstructed based on changes of the functional pufM gene. The use of functional genes together with rRNA genes may significantly expand the scientific potential of the ARNIS technique.

Aerobic anoxygenic phototrophs, Amplicon sequencing, Bacterioplankton, Grazing, Growth curves, Growth rate, Manipulation experiment, Phosphorus limitation, Top-down control

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