Ecophysiological interaction between nitrifying bacteria and heterotrophic bacteria in autotrophic nitrifying biofilms as determined by microautoradiography-fluorescence in situ hybridization

Kindaichi Tomonori

Ito Tsukasa

Okabe Satoshi

Applied and Environmental Microbiology

Ecophysiological interactions between the community members (i.e., nitrifiers and heterotrophic bacteria) in a carbon-limited autotrophic nitrifying biofilm fed only NH4+ as an energy source were investigated by using a full-cycle 16S RRNA approach followed by microautoradiography (MAR)-fluorescence in situ hybridization (FISH). Phylogenetic differentiation (identification) of heterotrophic bacteria was performed by 16S rRNA gene sequence analysis, and FISH probes were designed to determine the community structure and the spatial organization (i.e., niche differentiation) in the biofilm. FISH analysis showed that this autotrophic nitrifying biofilm was composed of 50% nitrifying bacteria (ammonia-oxidizing bacteria [AOB] and nitrite-oxidizing bacteria [NOB]) and 50% heterotrophic bacteria, and the distribution was as follows: members of the alpha subclass of the class Proteobacteria (α-Proteobacteria), 23%; γ-Proteobacteria, 13%; green nonsulfur bacteria (GNSB), 9%; Cytophaga-Flavobacterium-Bacteroides (CFB) division, 2%; and unidentified (organisms that could not be hybridized with any probe except EUB338), 3%. These results indicated that a pair of nitrifiers (AOB and NOB) supported a heterotrophic bacterium via production of soluble microbial products (SMP). MAR-FISH revealed that the heterotrophic bacterial community was composed of bacteria that were phylogenetically and metabolically diverse and to some extent metabolically redundant, which ensured the stability of the ecosystem as a biofilm. α- and γ -Proteobacteria dominated the utilization of [14C]acetic acid and 14C-amino acids in this biofilm. Despite their low abundance (ca. 2%) in the biofilm community, members of the CFB cluster accounted for the largest fraction (ca. 64%) of the bacterial community consuming N-acetyl-D-[1- 14C]glucosamine (NAG). The GNSB accounted for 9% of the 14C-amino acid-consuming bacteria and 27% of the [ 14C]NAG-consuming bacteria but did not utilize [14C] acetic acid. Bacteria classified in the unidentified group accoun

Construction. Civil engineering [ 510 ]

eng

American Society for Microbiology

Copyright (c) American Society for Microbiology

[ISSN] 0099-2240

[DOI] 10.1128/AEM.70.3.1641-1650.2004

[NCID] AA00543249

[DOI] http://dx.doi.org/10.1128/AEM.70.3.1641-1650.2004