Abundance and single‐cell activity of bacterial groups in Antarctic coastal waters

Abstract

We estimated the abundance and single-cell activity of bacterial groups in waters off the West Antarctic Peninsula (WAP) using a combination of microautoradiography and fluorescent in situ hybridization (FISH). The abundance of the Ant4D3 subgroup, detected by a new FISH probe, was 10% of the total community and half of the gammaproteobacterial population. The Ant4D3, Polaribacter, and SAR11 subgroups accounted for the majority of the Gammaproteobacteria, Sphingobacteria-Flavobacteria, and Alphaproteobacteria, respectively. Approximately 40% of the total microbial community actively incorporated leucine (added at 20 nmol L 21 ), while a smaller fraction (12-22%) used protein and an amino acid mixture (added at tracer concentrations). The fractions of SAR11, Polaribacter, and Ant4D3 that were active differed from each other and varied among substrates. SAR11 had the largest fraction of active cells incorporating leucine, while Polaribacter dominated the community using protein. The fraction of Ant4D3 using different compounds did not vary, but this group dominated the incorporation of amino acids, and was an abundant and active component of the bacterial community. Bacteria in the WAP region were as active as bacteria in the Mid-Atlantic Bight, even though total bacterial production was lower in the WAP. Though persistently cold (0-1uC) and dominated by different bacterial taxa, the single-cell activity of this summertime Antarctic bacterial community was comparable to that of temperate communities.

Distinct bacterial groups contribute to carbon cycling during a naturally iron fertilized phytoplankton bloom in the Southern Ocean

“…The enhanced activity of SAR92 in surface waters could possibly be linked to the presence of proteorhodopsin, as suggested previously (Stingl et al 2007). In the Western Arctic Peninsula, the subgroup ANT4D3 dominated Gammaproteobacteria (Straza et al 2010). This group was also present in our clone libraries from Sta.…”

“…The Roseobacter cluster RCA is reported to have global distribution with particularly high abundances in the Southern Ocean (Selje et al 2004). The subgroups RCA, SAR86, Agg58, and Polaribacter accounted each for up to 12% of bulk abundance in the Arctic Ocean, and Polaribacter contributed 10-22% to bulk abundance in coastal Antarctic waters (Malmstrom et al 2007;Straza et al 2010). These previous studies provide insight into spatial and temporal patterns of these bacterial groups; however, their ecological implications remain to be investigated.…”

“…These subgroups are members of the bacterial community in a variety of marine environments; however, only a few studies report on their quantitative contribution to abundance and activity in the polar oceans. The cosmopolitan SAR11 clade contributed up to 27% to bulk bacterial abundance in the Arctic Ocean and in Antarctic coastal waters, where this bacterial group also actively assimilated various organic compounds (Malmstrom et al 2007;Straza et al 2010). The Roseobacter cluster RCA is reported to have global distribution with particularly high abundances in the Southern Ocean (Selje et al 2004).…”

Bacterial uptake of low molecular weight organics in the subtropical Atlantic: Are major phylogenetic groups functionally different?

“…Similarly, the biosynthetic activity of SAR11 and a group of Rhodobacteraceae (RCA cluster) increased toward shelf waters in the same system (Malmstrom et al 2007). In a study along the West Antarctic Peninsula that analyzed the uptake of amino acids at tracer concentrations, Polaribacter also increased their activity from offshore to coastal waters and no significant differences were found for the activity of SAR11 across that marine gradient (Straza et al 2010). …”

Response of a summertime Antarctic marine ­bacterial community to glucose and ammonium enrichment

“…Murray et al (1998) demonstrated a strong, repeatable seasonal cycle of the BCC at Palmer Stn, Antarctica, and later showed that the late winter community comprised -in about equal proportions -Alphaproteobacteria, Gammaproteobacteria and members of the Cytophaga-Flavobacteria-Bacteroidetes (CFB) group (Murray & Grzymski 2007). These same 3 groups also dominated the midsummer bacterial assemblage, each group contributing about one-third of the total standing stock of bacteria (Straza et al 2010). However, how these changes are related to the parallel variability of bacterial carbon cycling is not known.…”