Growth and productivity of phytoplankton substantially change organic matter characteristics, which affect bacterial abundance, productivity, and community structure in aquatic ecosystems. We analyzed bacterial community structures and measured activities inside and outside phytoplankton blooms in the western North Pacific Ocean by using bromodeoxyuridine immunocytochemistry and fluorescence in situ hybridization (BIC-FISH). Roseobacter/Rhodobacter, SAR11, Betaproteobacteria, Alteromonas, SAR86, and Bacteroidetes responded differently to changes in organic matter supply. Roseobacter/Rhodobacter bacteria remained widespread, active, and proliferating despite large fluctuations in organic matter and chlorophyll a (Chl-a) concentrations. The relative contribution of Bacteroidetes to total bacterial production was consistently high. Furthermore, we documented the unexpectedly large contribution of Alteromonas to total bacterial production in the bloom. Bacterial abundance, productivity, and growth potential (the proportion of growing cells in a population) were significantly correlated with Chl-a and particulate organic carbon concentrations. Canonical correspondence analysis showed that organic matter supply was critical for determining bacterial community structures. The growth potential of each bacterial group as a function of Chl-a concentration showed a bell-shaped distribution, indicating an optimal organic matter concentration to promote growth. The growth of Alteromonas and Betaproteobacteria was especially strongly correlated with organic matter supply. These data elucidate the distinctive ecological role of major bacterial taxa in organic matter cycling during open ocean phytoplankton blooms.The major ecological function of heterotrophic bacteria in interactions with phytoplankton is mineralization of organic matter for recycling of nutrients and secondary production, which is channeled mainly to the higher trophic levels of aquatic food webs (10, 66). Growth of phytoplankton leads to major changes in organic matter quantity and quality, which results in changes to bacterial community structure, abundance, and productivity (3). Previous studies have shown that bacterial abundance, production, and community structure change markedly during naturally occurring and experimentally induced phytoplankton blooms (16,56,61). These studies pointed to several key phylogenetic groups as actively responding to the blooms and utilizing organic matter derived from phytoplankton. Bacteroidetes and Alpha-and Gammaproteobacteria were reportedly important during the blooms. Their relative contributions to total bacterial abundance and its variability have been studied intensively by using fluorescence in situ hybridization (FISH). However, as abundance is determined by both growth and mortality, changes in bacterial abundance do not always indicate changes in growth. Mainly because of some methodological limitations, little is known about the relative contributions of these key groups to total bacterial production or its va...
A fundamental question in microbial oceanography concerns the relationship between prokaryote diversity and biogeochemical function in an ecosystem context. We combined bromodeoxyuridine (BrdU) magnetic bead immunocapture and PCR-denaturing gradient gel electrophoresis (BUMP-DGGE) to examine phylotype-specific growth in natural marine assemblages. We also examined a broad range of marine bacterial isolates to determine their abilities to incorporate BrdU in order to test the validity of the method for application to diverse marine assemblages. We found that 27 of 29 isolates belonging to different taxa could incorporate BrdU. BUMP-DGGE analysis revealed phylogenetic affiliations of DNA-synthesizing, presumably actively growing bacteria across a eutrophic to mesotrophic transect in the Inland Sea of Japan. We found that the BrdU-incorporating (growing) communities were substantially different from the total communities. The majority (34/56) of phylotypes incorporated BrdU and were presumably growing, and these phylotypes comprised 10 alphaproteobacteria, 1 betaproteobacterium, 11 gammaproteobacteria, 11 Cytophaga-Flavobacterium-Bacteroides group bacteria, and 1 unclassified bacterium. All BrdU-responsive alphaproteobacteria were members of the Rhodobacterales, suggesting that such bacteria were dominant in the growing alphaproteobacterial populations in our samples. The BrdU-responsive gammaproteobacteria belonged to the Oceanospirillales, the SAR86 cluster, the Pseudomonadales, the Alteromonadales, and the Vibrionales. Thus, contemporaneous cooccurrence of diverse actively growing bacterial taxa was a consistent pattern in our biogeochemically varied study area.Bacteria in seawater play important roles in the ocean's food webs. Their activities and responses to organic substrates significantly influence the flux of organic matter and oceanic biogeochemical cycles (3, 4). Because only a small fraction of bacteria in any seawater sample can be isolated and cultivated, culture-independent methods employing molecular approaches have been used to great advantage during the last two decades to study the natural assemblages of marine bacteria (11,19,39). These and other studies have revealed unexpected diversity and dynamics of bacterial community structure in seawater (8,16,47). However, the great challenge remains to relate diversity to ecological function and biogeochemical activities of bacteria. In recent studies workers have combined fluorescence in situ hybridization (FISH) with microautoradiography and found differences in the uptake of specific organic substrates by different phylogenetic groups of bacteria (7,8,40). Stable-isotope probing has enabled PCR-based DNA analysis of bacteria that incorporate specific substrates (45).Bromodeoxyuridine (BrdU), a halogenated nucleoside that can serve as a thymidine (TdR) analog, has been widely used as an alternative to tritiated TdR ([ 3 H]TdR) incorporation to label proliferating cells in cell biology (2, 59). BrdU incorporated into de novo DNA can be detected using ...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.