ISSN:
1432-184X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Two approaches employing 16S rRNA oligonucleotide probes, in situ hybridization combined with 33P-autoradiography and 32P-labeled slot-blot hybridizations on nitrocellulose filters, were used to enumerate methylotrophic bacteria in the water column of Ryans 1 Billabong, a small floodplain lake in northeastern Victoria, Australia. Methylotrophic bacterioplankton numbered 0.6–1.2 × 109 cells liter−1 in the winter of 1994, and 0.8–5.5 × 109 cells liter−1 in the summer of 1994–95. This was equivalent to 10–46% of total bacterioplankton cell counts, determined via epifluorescence microscopy. Methylotrophic bacteria were not detected in the water column of the nearby Kiewa River, and a set of laboratory controls indicated that the high abundance of methylotrophs in the billabong samples was not a methodological artifact. There was no change, with water depth, in total bacterioplankton or methylotroph abundance in winter, a result consistent with the water column being well mixed at this time of year (dissolved O2 concentrations 5–7 mg liter−1; dissolved methane concentrations 〈60 μg liter−1, or 〈5% methane saturation, at all depths). In summer the billabong became diurnally stratified (dissolved O2 concentrations 〈2 mg liter−1 at water depths of 〉45 cm; dissolved methane concentrations 〈100 μg liter−1 at the surface, but 〉500 μg liter−1 near the sediments) and there was a correspondingly marked increase in the abundance of total bacterioplankton and methylotrophs with depth. In situ hybridizations and slot-blot hybridizations both indicated that type II methylotrophs (detected with a probe specific for the 9-α subgroup of Proteobacteria) were markedly less abundant than were type I and X methylotrophs (detected with a probe specific for the 10-γ subgroup of Proteobacteria).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002489900039
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