ISSN 2736-1756
Advanced Journal of Microbiology Research ISSN 2241-9837 Vol. 12 (4), pp. 001-008, April, 2018. © International Scholars Journals
Full Length Research Paper
Microbial morphology and community structure in a suspended carrier biofilm reactor as a function of substrate loading rates
Fu Bo1, 2, Liao Xiaoyi1, Ding Lili1, Xu Ke1 and Ren Hongqiang1*
1State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093, Jiangsu, China.
2Laboratory of Environmental Biotechnology, School of Environmental and Civil Engineering, Jiangnan University, Wuxi 214122, Jiangsu, China.
Accepted 13 January, 2018
Abstract
An aerobic suspended carrier biofilm reactor was efficient in simultaneous organic carbon and nitrogen removal, with COD removal efficiencies of 87.1–99.0% and simultaneous nitrification and denitrification (SND) efficiencies about 96.7-98.8%. The effects of substrate loading on microbial morphology and community structure were investigated by environmental scanning electron microscopy (ESEM), denaturing gel gradient electrophoresis (DGGE) and fluorescence in situ hybridization (FISH). Biofilms formed at different substrate loadings had different morphology and community structures. A higher substrate concentration resulted in denser and thinner biofilms, while a lower substrate concentration resulted in looser and thicker biofilms with significant presence of filamentous bacteria. Both sequence analysis of DGGE bands and FISH analysis indicated the dominance of β-Proteobacteria in the biofilm communities, especially Zoogloea. FISH analysis revealed that the relative abundance of β-proteobacteria ammonia oxidizing bacteria (AOB) was positively correlated with ammonium concentrations, whereas Nitrospira-like nitrite-oxidizing bacteria (NOB) were negatively affected by ammonia and nitrite concentrations. The presence of denitrifying bacteria, Hydrogenophaga spp., Hyphomicrobium spp. and Rhizobium spp. suggested that not only the oxygen microgradients within the biofilm but also aerobic denitrifiers may be responsible for SND in the aerobic biofilm.
Key words: Microbial community structure, microbial morphology, substrate loading, suspended carrier biofilm.