Satoshi Okabe

We investigated the in situ spatial organization of ammonia-oxidizing and nitrite-oxidizing bacteria in domestic wastewater biofilms and autotrophic nitrifying biofilms by using microsensors and fluorescent in situ hybridization (FISH) performed with 16S rRNA-targeted oligonucleotide probes. The combination of these techniques made it possible to relate in situ microbial activity directly to the occurrence of nitrifying bacterial populations. In situ hybridization revealed that bacteria belongin

Microbially induced concrete corrosion (MICC) in sewer systems has been a serious problem for a long time. A better understanding of the succession of microbial community members responsible for the production of sulfuric acid is essential for the efficient control of MICC. In this study, the succession of sulfur-oxidizing bacteria (SOB) in the bacterial community on corroding concrete in a sewer system in situ was investigated over 1 year by culture-independent 16S rRNA gene-based molecular tec

Biofilms are considered to be highly resistant to antimicrobial agents. Several mechanisms have been proposed to explain this high resistance of biofilms, including restricted penetration of antimicrobial agents into biofilms, slow growth owing to nutrient limitation, expression of genes involved in the general stress response, and emergence of a biofilm-specific phenotype. However, since combinations of these factors are involved in most biofilm studies, it is still difficult to fully understan

To date, six candidate genera of anaerobic ammonium-oxidizing (anammox) bacteria have been identified, and numerous studies have been conducted to understand their ecophysiology. In this study, we examined the physiological characteristics of an anammox bacterium in the genus 'Candidatus Jettenia'. Planctomycete KSU-1 was found to be a mesophilic (20-42.5°C) and neutrophilic (pH 6.5-8.5) bacterium with a maximum growth rate of 0.0020 h(-1) . Planctomycete KSU-1 cells showed typical physiological

The vertical distribution of sulfate-reducing bacteria (SRB) in aerobic wastewater biofilms grown on rotating disk reactors was investigated by fluorescent in situ hybridization (FISH) with 16S rRNA-targeted oligonucleotide probes. To correlate the vertical distribution of SRB populations with their activity, the microprofiles of O(2), H(2)S, NO(2)(-), NO(3)(-), NH(4)(+), and pH were measured with microelectrodes. In addition, a cross-evaluation of the FISH and microelectrode analyses was perfor

The cross-feeding of microbial products derived from 14C-labeled nitrifying bacteria to heterotrophic bacteria coexisting in an autotrophic nitrifying biofilm was quantitatively analyzed by using microautoradiography combined with fluorescence in situ hybridization (MAR-FISH). After only nitrifying bacteria were labeled with [14C]bicarbonate, biofilm samples were incubated with and without NH4+ as a sole energy source for 10 days. The transfer of 14C originally incorporated into nitrifying bacte

We investigated autotrophic anaerobic ammonium-oxidizing (anammox) biofilms for their spatial organization, community composition, and in situ activities by using molecular biological techniques combined with microelectrodes. Results of phylogenetic analysis and fluorescence in situ hybridization (FISH) revealed that "Brocadia"-like anammox bacteria that hybridized with the Amx820 probe dominated, with 60 to 92% of total bacteria in the upper part (<1,000 microm) of the biofilm, where high anamm

Spatial microbial distributions of nitrifiers and heterotrophs in undefined mixed-population biofilms were experimentally investigated using a microslicer technique and correlated with nitrification efficiency of the biofilm system. The general stratification of different bacterial groups in the biofilm was simulated using a one-dimensional (1-D) mathematical biofilm accumulation model (BAM) and compared with the experimental results. Biofilms were cultured at three C : N ratios of feed solution