Premium
Analysis of size distribution and areal cell density of ammonia‐oxidizing bacterial microcolonies in relation to substrate microprofiles in biofilms
Author(s) -
Okabe Satoshi,
Kindaichi Tomonori,
Ito Tsukasa,
Satoh Hisashi
Publication year - 2003
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.10864
Subject(s) - biofilm , autotroph , nitrosomonas europaea , substrate (aquarium) , biology , nitrosomonas , bacteria , heterotroph , environmental chemistry , chemistry , microbiology and biotechnology , ecology , nitrate , nitrite , genetics
A fine‐scale in situ spatial organization of ammonia‐oxidizing bacteria (AOB) in biofilms was investigated by combining molecular techniques (i.e., fluorescence in situ hybridization (FISH) and 16S rDNA‐cloning analysis) and microelectrode measurements. Important parameters of AOB microcolonies such as size distribution and areal cell density of the microcolonies were determined and correlated with substrate microprofiles in the biofilms. In situ hybridization with a nested 16S rRNA‐targeted oligonucleotide probe set revealed two different populations of AOB, Nitrosomonas europaea ‐lineage and Nitrosospira multiformis ‐lineage, coexisting in an autotrophic nitrifying biofilm. Nitrosospira formed looser microcolonies, with an areal cell density of 0.51 cells μm −2 , which was half of the cell density of Nitrosomonas (1.12 cells μm −2 ). It is speculated that the formation of looser microcolonies facilitates substrate diffusion into the microcolonies, which might be a survival strategy to low O 2 and NH 4 +conditions in the biofilm. A long‐term experiment (4‐week cultivation at different substrate C/N ratios) revealed that the size distribution of AOB microcolonies was strongly affected by better substrate supply due to shorter distance from the surface and the presence of organic carbon. The microcolony size was relatively constant throughout the autotrophic nitrifying biofilm, while the size increased by ∼80% toward the depth of the biofilm cultured at the substrate C/N = 1. A short‐term (∼3 h) organic carbon addition experiment showed that the addition of organic carbon created interspecies competition for O 2 between AOB and heterotrophic bacteria, which dramatically decreased the in situ NH 4 + ‐uptake activity of AOB in the surface of the biofilms. This result might explain the spatial distribution of AOB microcolony size in the biofilms cultured at the substrate C/N = 1. These experimental results suggest O 2 and organic carbon were the main factors controlling the spatial organization and activity of AOB in biofilms. These findings are significantly important to further improve mathematical models used to describe how the slow‐growing AOB develop their niches in biofilms and how that configuration affects nitrification performance in the biofilm. © 2003 Wiley Periodicals, Inc.