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Appl. Environ. Microbiol., 11 1997, 4164-4170, Vol 63, No. 11
S Kalmbach, W Manz and U Szewzyk
A polyphasic approach involving cultivation, direct viable counts, rRNA-
based phylogenetic classification, and in situ probing was applied for the
characterization of the dominant microbial population in a municipal
drinking water distribution system. A total of 234 bacterial strains
cultivated on R2A medium were screened for bacteria affiliated with the in
situ dominating beta subclass of Proteobacteria. The isolates were grouped
according to common features of their cell and colony morphologies, and
eight representative strains were used for 16S rRNA sequencing and the
development of a suite of strain-specific oligonucleotide probes.
Phylogenetic analysis indicated that all of the isolates were hitherto
unknown bacteria. Three of them, strains B4, B6, and B8, formed a separate
cluster of closely related organisms within the beta 1 subclass of
Proteobacteria. In situ probing revealed that (i) 67 to 72% of total
bacteria, corresponding to more than 80% of beta- subclass bacteria, could
be encompassed with the strain-specific probes and (ii) the dominating
bacterial species were culturable on R2A medium. Additionally, two-thirds
of the autochthonous drinking water population could be shown to be in a
viable but nonculturable (VBNC) state by using a direct viable count
approach. The comparison of isolation frequencies with the in situ
abundances of the eight investigated strains revealed differences in their
culturability, indicating variable ratios of culturable to VBNC cells among
the strains. The further characterization of biofilms throughout the
distribution network demonstrated strains B6 and B8 to be dominant
bacterial strains in groundwater and distribution system biofilms. The
other strains could be found at various frequencies in the different parts
of the distribution system; several strains appeared exclusively in
drinking water biofilms obtained from a house installation system.
Copyright © 1997, American Society for Microbiology
Isolation of new bacterial species from drinking water biofilms and proof of their in situ dominance with highly specific 16S rRNA probes
Fachgebiet Okologie der Mikroorganismen, Institut fur Technischen Umweltschutz, Technische Universitat Berlin, Germany.
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