Isolation and characterization of Arthrobacter sp. from activated sludge of a pulp and paper mill

The bacterial population from activated sludge samples of a pulp and paper mill was investigated. Analysis of colonies on plates count, including Gram stain, cells and colonies morphology, cytochrome oxidase and catalase reactions, revealed the presence of four main bacterial groups with a major one. The presence of this main population (24.90% to 64.80% of the total population) was followed during one year at the rate of one two-months sampling. The taxonomic study of several isolates and use of rRNA-targeted oligonucleotide probes led to the identification of Arthrobacter sp., with a marked rod-coccus Gram-positive growth cycle, catalase-positive and oxidase-negative reactions and obligately aerobic non-motile cells. L-lysine was identified in the cell wall peptidoglycan and the % G+C of the DNA was about 72.0 (Tm). The presence of Arthrobacter sp. in the wastewater treatment system had a singular character. Moreover, these bacteria were devoid of cellulolytic, amylolytic and proteolytic activities. The preservation of biofloc efficiency seems to be the main function of these bacteria.