Prevalence of Proteobacteria and Armatimonadetes phyla in a Photobioreactor under Carbon- and Nitrogen-Free Production Process

Abstract

In prokaryotes, the autotrophic population within the bacteria kingdom carries great biotechnological potential. For taxonomic analysis of species, the sequence encoding the small subunit ribosomal RNA gene (16S rRNA) is currently the most reliable technique for phylogenetic bacterial classification. Sequencing can define the population diversity and ecological importance within a habitat. The study of autotrophic bacteria population dynamics in a photobioreactor using a carbon-and nitrogen-free culture medium could provide information about succession dynamics under controlled conditions. The aim of this study was to identify the bacterial populations present in a photobioreactor by 16S rRNA amplicon sequence comparison from samples taken at 0, 7, and 14 fermentation days. Most of the identified clones were described to the level of genera from the following phyla: Proteobacteria (40%), Armatimonadetes (35%), Firmicutes (17.5%), Actinobacteria (2.5%), and Cyanobacteria/Chloroplast (2.5%). Bacterial strains from such phyla have been reported in aquatic environments and were considered uncultivable; however, sequences indicated the presence of the clones A-123 (ID: HQ860522.1) from time 0, and YHS25 (GU305825.1) after 7 days of culture. Our findings demonstrated the major presence of autotrophic bacterial populations of the Proteobacteria and Armatimonadetes phyla, which grew under artificial culture conditions in a photobioreactor.