Quantitative fluorescent in-situ hybridization: a hypothesized competition mode between two dominant bacteria groups in hydrogen-producing anaerobic sludge processes

摘要

Two hydrogen-producing continuous flow stirred tank reactors (CSTRs) fed respectively withnglucose and sucrose were investigated by polymerase chain reaction-denatured gradient gelnelectrophoresis (PCR-DGGE) and fluorescent in-situ hybridization (FISH). The substrate was fed in ancontinuous mode decreased from hydraulic retention time (HRT) 10 hours to 6, 5, 4, 3, and 2nhours. Quantitative fluorescent in-situ hybridization (FISH) observations further demonstrated thatntwo morphotypes of bacteria dominated both microbial communities. One was long rod bacterianwhich can be targeted either by Chis150 probe designed to hybridize the gram positive low G + Cnbacteria or the specific oligonucleotide probe Lg10-6. The probe Lg10-6, affiliated with Clostridiumnpasteurianum, was designed and then checked with other reference organisms. The other type,nunknown group, which cannot be detected by Chis150 was curved rod bacteria. Notably, thenpopulation ratios of the two predominant groups reflected the different operational performancenof the two reactors, such as hydrogen producing rates, substrate turnover rates and metabolitesncompositions. Therefore, a competition mode of the two dominant bacteria groups wasnhypothesized. In the study, 16S rRNA-based gene library of hydrogen-producing microbialncommunities was established. The efficiency of hydrogen yields was correlated with substratesn(glucose or sucrose), HRT, metabolites compositions (acetate, propionate, butyrate and ethanol),nthermal pre-treatment (seed biomass was heated at 1008C for 45 minutes), and microbialncommunities in the bioreactor, not sludge sources (municipal sewage sludge, alcohol-processingnsludge, or bean-processing sludge). The designed specific oligonucleotide probe Lg10-6 alsonprovides us a useful and fast molecular tool to screen hydrogen-producing microbial communitiesnin the future research.