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Colonization of overlaying water by bacteria from dry river sediments
Author(s) -
Fazi Stefano,
Amalfitano Stefano,
Piccini Claudia,
Zoppini Annamaria,
Puddu Alberto,
Pernthaler Jakob
Publication year - 2008
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/j.1462-2920.2008.01695.x
Subject(s) - biology , alphaproteobacteria , bacteria , 16s ribosomal rna , microbial population biology , microbiology and biotechnology , bacteroidetes , leucyl aminopeptidase , gammaproteobacteria , leucine , aminopeptidase , biochemistry , amino acid , genetics
Summary We studied the diversity, community composition and activity of the primary microbial colonizers of the water above freshly re‐wetted sediments from a temporary river. Dried sediments, collected from Mulargia River (Sardinia, Italy), were covered with sterile freshwater in triplicate microcosms, and changes of the planktonic microbial assemblage were monitored over a 48 h period. During the first 9 h bacterial abundance was low (1.5 × 10 4 cells ml −1 ); it increased to 3.4 × 10 6 cells ml −1 after 28 h and did not change thereafter. Approximately 20% of bacteria exhibited DNA de novo synthesis already after 9 h of incubation. Changes of the ratios of 3 H‐leucine to 3 H‐thymidine incorporation rates indicated a shift of growth patterns during the experiment. Extracellular enzyme activity showed a maximum at 48 h with aminopeptidase activity (430.8 ± 22.6 nmol MCA l −1 h −1 ) significantly higher than alkaline phosphatase (98.6 ± 4.3 nmol MUF l −1 h −1 ). The primary microbial colonizers of the overlaying water – as determined by 16S rRNA gene sequence analysis – were related to at least six different phylogenetic lineages of Bacilli and to Alphaproteobacteria ( Brevundimonas spp. and Caulobacter spp.). Large bacterial cells affiliated to one clade of Bacillus sp. were rare in the dried sediments, but constituted the majority of the planktonic microbial assemblage and of cells with detectable DNA‐synthesis until 28 h after re‐wetting. Their community contribution decreased in parallel with a rise of flagellated and ciliated protists. Estimates based on cell production rates suggested that the rapidly enriched Bacillus sp. suffered disproportionally high loss rates from selective predation, thus favouring the establishment of a more heterogenic assemblage of microbes (consisting of Proteobacteria , Actinobacteria and Cytophaga‐Flavobacteria ) . Our results suggest that the primary microbial colonizers of the water above dried sediments are passively released into the plankton and that their high growth potential is counteracted by the activity of bacterivorous protists.