Changes in community composition during dilution cultures of marine bacterioplankton as assessed by flow cytometric and molecular biological techniques

Abstract

Dilution cultures are a common technique for measuring the growth of bacterioplankton communities. In this study, the taxonomic composition of marine bacterioplankton dilution cultures was followed in water samples from Plymouth Sound and the English Channel (UK). Bacterial abundances as well as protein and DNA content were closely monitored by flow cytometry. Denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR)-amplified 16S rDNA fragments and fluorescence in situ hybridization (FISH) were applied directly to the water samples and to cells sorted from the dilution cultures based on their protein and DNA content. As expected, a rapid activation of bacteria occurred. However, molecular techniques showed that the community developed in the dilution culture within 1 day was significantly different from that in the original water samples. Whereas in the original samples, cells detectable by FISH were dominated by members of the Cytophagal Flavobacterium (CF) cluster, in dilution cultures, gamma-proteobacteria accounted for the majority of cells detected, followed by alpha-proteobacteria. An actively growing and an apparently non-growing population with average cellular protein contents of 24 and 4.5 fg respectively, were sorted by flow cytometry. FISH indicated mostly gamma- (64%) and alpha-proteobacteria (33%) in the first active fraction and 78% members of the CF cluster in the second fraction. Sequencing of DGGE bands confirmed the FISH assignments of the latter two groups. The data presented clearly show that even relatively short-term dilution experiments do not measure in situ growth, but rather growth patterns of an enrichment. Furthermore, it was demonstrated that the combination of flow cytometric analysis and sorting combined with FISH and DGGE analysis presented a fairly rapid method of analysing the taxonomic composition of marine bacterioplankton.

Disentangling the relative influence of bacterioplankton phylogeny and metabolism on lysogeny in reservoirs and lagoons

“…(ii) The intrinsic low activity of a bacterial group may only allow lysogeny. The Bacteroidetes have been repeatedly found to grow more slowly than other phylogenetic groups (Fuchs et al, 2000;Simek et al, 2001;Zubkov et al, 2001, this study). This metabolic feature may thus represent a signal for the establishment of lysogeny.…”

Responses of the coastal bacterial community to viral infection of the algae Phaeocystis globosa

“…Further, viral-mediated P. globosa lysis promoted the growth of opportunistic Gamma-and Alphaproteobacteria (r-strategists) relative to slow growing bacteria (for example, Bacteroidetes, K-strategists) (Fuchs et al, 2000). The bacterial community composition also changed in association with aging P. globosa cells from non-infected control cultures.…”

Function-specific response to depletion of microbial diversity

“…Natural lake water contains a large variety of organic compounds (Perdue, 2009) and there is also a large variety in bacterial ability to synthesize enzymes for substrate utilization and biomass production. In mixed batch cultures, bacterial growth follows reproducible trajectories (Ammerman et al, 1984;Tranvik and Höfle, 1987) and maintains similar growth-related functions independently of the source of inoculum (Fuchs et al, 2000;Gasol et al, 2002;Langenheder et al, 2005Langenheder et al, , 2006. This can be explained either by similarly composed communities emerging in those cultures or by differently composed communities maintaining similar functions.…”