title: Microbial community structure and diversity in an integrated system of anaerobic-aerobic reactors and a constructed wetland for the treatment of tannery wastewater in Modjo, Ethiopia.
abstract: A culture-independent approach was used to elucidate the microbial diversity and structure in the anaerobic-aerobic reactors integrated with a constructed wetland for the treatment of tannery wastewater in Modjo town, Ethiopia. The system has been running with removal efficiencies ranging from 94%-96% for COD, 91%-100% for SO4(2-) and S(2-), 92%-94% for BOD, 56%-82% for total Nitrogen and 2%-90% for NH3-N. 16S rRNA gene clone libraries were constructed and microbial community assemblies were determined by analysis of a total of 801 unique clone sequences from all the sites. Operational Taxonomic Unit (OTU)--based analysis of the sequences revealed highly diverse communities in each of the reactors and the constructed wetland. A total of 32 phylotypes were identified with the dominant members affiliated to Clostridia (33%), Betaproteobacteria (10%), Bacteroidia (10%), Deltaproteobacteria (9%) and Gammaproteobacteria (6%). Sequences affiliated to the class Clostridia were the most abundant across all sites. The 801 sequences were assigned to 255 OTUs, of which 3 OTUs were shared among the clone libraries from all sites. The shared OTUs comprised 80 sequences belonging to Clostridiales Family XIII Incertae Sedis, Bacteroidetes and unclassified bacterial group. Significantly different communities were harbored by the anaerobic, aerobic and rhizosphere sites of the constructed wetland. Numerous representative genera of the dominant bacterial classes obtained from the different sample sites of the integrated system have been implicated in the removal of various carbon- containing pollutants of natural and synthetic origins. To our knowledge, this is the first report of microbial community structure in tannery wastewater treatment plant from Ethiopia.
authors.affiliation: Institute of Biotechnology, Addis Ababa University, Addis Ababa, Ethiopia.
authors.forename: Adey Feleke
authors.initials: AF
authors.lastname: Desta
authors.affiliation: Institute of Biotechnology, Addis Ababa University, Addis Ababa, Ethiopia.
authors.forename: Fassil
authors.initials: F
authors.lastname: Assefa
authors.affiliation: Centre for Environmental Science, College of Natural Sciences, Addis Ababa University, Addis Ababa, Ethiopia.
authors.forename: Seyoum
authors.initials: S
authors.lastname: Leta
authors.affiliation: Biosciences eastern and central Africa- International Livestock Research Institute (BecA-ILRI) Hub, Nairobi, Kenya.
authors.forename: Francesca
authors.initials: F
authors.lastname: Stomeo
authors.affiliation: Biosciences eastern and central Africa- International Livestock Research Institute (BecA-ILRI) Hub, Nairobi, Kenya.
authors.forename: Mark
authors.initials: M
authors.lastname: Wamalwa
authors.affiliation: Biosciences eastern and central Africa- International Livestock Research Institute (BecA-ILRI) Hub, Nairobi, Kenya.
authors.forename: Moses
authors.initials: M
authors.lastname: Njahira
authors.forename: Appolinaire
authors.initials: A
authors.lastname: Djikeng
authors.affiliation: Biosciences eastern and central Africa- International Livestock Research Institute (BecA-ILRI) Hub, Nairobi, Kenya.
authors.forename: Djikeng
authors.initials: D
authors.lastname: Appolinaire
mesh_terms: D001419:Bacteria / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D005002:Ethiopia; D015723:Gene Library; D008969:Molecular Sequence Data; D010802:Phylogeny; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D062065:Wastewater / Q000382:microbiology*; D018508:Water Purification / Q000379:methods; D053833:Wetlands
chemical_list: D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D062065:Wastewater