Abstract
The bacterial community structure of the activated sludge from a 25 million-gal-per-day industrial wastewater treatment plant was investigated using rRNA analysis. 16S ribosomal DNA (rDNA) libraries were created from three sludge samples taken on different dates. Partial rRNA gene sequences were obtained for 46 rDNA clones, and nearly complete 16S rRNA sequences were obtained for 18 clones. Seventeen of these clones were members of the beta subdivision, and their sequences showed high homology to sequences of known bacterial species as well as published 16S rDNA sequences from other activated sludge sources. Sixteen clones belonged to the alpha subdivision, 7 of which showed similarity to Hyphomicrobium species. This cluster was chosen for further studies due to earlier work on Hyphomicrobium sp. strain M3 isolated from this treatment plant. A nearly full-length 16S rDNA sequence was obtained from Hyphomicrobium sp. strain M3. Phylogenetic analysis revealed that Hyphomicrobium sp. strain M3 was 99% similar to Hyphomicrobium denitrificans DSM 1869(T) in Hyphomicrobium cluster II. Three of the cloned sequences from the activated sludge samples also grouped with those of Hyphomicrobium cluster II, with a 96% sequence similarity to that of Hyphomicrobium sp. strain M3. The other four cloned sequences from the activated sludge sample were more closely related to those of the Hyphomicrobium cluster I organisms (95 to 97% similarity). Whole-cell fluorescence hybridization of microorganisms in the activated sludge with genus-specific Hyphomicrobium probe S-G-Hypho-1241-a-A-19 enhanced the visualization of Hyphomicrobium and revealed that Hyphomicrobium appears to be abundant both on the outside of flocs and within the floc structure. Dot blot hybridization of activated sludge samples from 1995 with probes designed for Hyphomicrobium cluster I and Hyphomicrobium cluster II indicated that Hyphomicrobium cluster II-positive 16S rRNA dominated over Hyphomicrobium cluster I-positive 16S rRNA by 3- to 12-fold. Hyphomicrobium 16S rRNA comprised approximately 5% of the 16S rRNA in the activated sludge.
Highlights
Activated sludge, a common biological treatment method for both municipal and industrial wastewater, represents a complex microbial community
Preliminary analysis based on sequences using the 1492r or 27f primers was performed on 67 16S ribosomal DNA (rDNA) clones from three different sludge samples taken from the same industrial wastewater treatment plant
The cloned 16S rDNAs were assigned to Eubacteria groups and Proteobacteria subdivisions (Table 3)
Summary
A common biological treatment method for both municipal and industrial wastewater, represents a complex microbial community. The microbial community from an activated sludge system used to treat wastewater from chemical manufacturing processes was examined. This differs from municipal wastewater in that it is much higher in its total organic carbon load, comprising mostly simple organic acids and alcohols, with little fibrous or complex carbon sources present. Other researchers [5, 33, 37] have proposed that a combination of approaches is needed to understand the basic microbial community structure of activated sludge These methods include the construction and analysis of 16S rDNA libraries, hybridization with rRNA-targeted oligonucleotides, and comparison of those results with a specific focus on the presence of Hyphomicrobium-like strains
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
