Heterotrophic nitrogen removal bacteria in piggery wastes in the Mekong Delta, Vietnam

A total of 2318 heterotrophic nitrogen removal (HNR) bacteria isolated from piggery wastes (after biogas container) were classified in four kinds of heterotrophic ammonia-oxidizing bacteria (569 isolates), nitrite-oxidizing bacteria (580 isolates), nitrate-oxidizing bacteria (600 isolates) and heterotrophic nitrifying and denitrifying bacteria (569 isolates). The virtually complete 16S rRNA gene was PCR amplified and sequenced. The sequences from the selected HNR bacteria showed high degrees of similarity to those of the GenBank references strains (between 97% and 99.8%). Phylogenetic trees based on the 16S rDNA sequences displayed high consistency, with nodes supported by high bootstrap (500) values. These presumptive HNR isolates were divided four groups that included members of genera Arthrobacter, Corynebacterium, Rhodococcus (high G+C content gram-positive bacteria), Staphylococcus, Bacillus (low G+C content gram-positive bacteria) and Klebsiella (gram-negative bacteria). Based on Pi value (nucleotide diversity), heterotrophic ammonium-oxidizing bacteria group had highest values and heterotrophic nitrifying-denitrifying bacteria group had the lowest values and Theta values (per sequence) from S of SNP for DNA polymorphism showed that heterotrophic nitrate-oxidizing bacteria group had the highest theta values in comparison of three groups. The present study, the HNR bacteria from piggery wastes, showed a very diverse community of HNR bacteria with a relatively high number of species involved in solid-wastewater samples and many isolates have nitrogen utilization ability at high concentration (800 – 1200 mM) and high G+C gram-positive bacteria strain occupied higher than low G+C gram-positive bacteria strain.