Performance of Aerobic Denitrification by the Strain Pseudomonas balearica RAD-17 in the Presence of Antibiotics

Aerobic denitrification, one of the important nitrate metabolic pathways in biological denitrification, has been attracting increasing interest recently due to its functional advantages. In order to evaluate the effect of antibiotics on aerobic denitrification and guide practical engineering application of aerobic denitrification techniques, we evaluated the performance of aerobic denitrification by the strain Pseudomonas balearica RAD-17 in the presence of ciprofloxacin (CFX) and oxytetracycline (OTC). No significant negative impact on the performance of aerobic denitrification in the presence of CFX or OTC within the range of 50 to 300 μg L−1 was found. Significant degradation of OTC was found within the range of 50 μg L−1 to 300 μg L−1 under aerobic denitrification conditions, while no degradation was found for CFX. Stimulation of cell growth occurred within the investigated range of antibiotics. Under anoxic or aerobic conditions, the addition of CFX or OTC changed the N2O production trend. The results in the present study may play an important role in informing the use of aerobic denitrification techniques in the presence of antibiotics within environmentally relevant concentrations (<1 mg/L).

Use of Taguchi Design for Optimization of Diesel-oil Biodegradation Using Consortium of Pseudomonas Stutzeri, Cellulosimicrobium Cellulans, Acinetobacter Baumannii and Pseudomonas Balearica Isolated From Tarball in Terengganu Beach, Malaysia

Consortium of bacteria capable of degrading oily hydrocarbons were isolated from tarball on beaches in Terengganu, Malaysia and classified as Pseudomonas stutzeri, Cellulosimicrobium cellulans, Acinetobacter baumannii and Pseudomonas balearica. Taguchi design was used to optimize diesel-oil biodegradation using these bacteria as consortium. Maximum diesel-oil biodegradation by experimental runs was 93.6% with individual n-alkanes degraded between 87.6% – 97.6% in 30 days. Optimal settings were 2.5 mL (1.248 OD600nm) inoculum size; 12% (v/v) initial diesel-oil in minimal salt media with 7.0 pH, 30.0 gL-1 NaCl and 2.0 gL-1 NH4NO3 concentration, incubated at 42oC temperature and 150 rpm agitation speed. Parameters significantly improved diesel-oil removal by consortium as indicated by model determination coefficient (R2 = 90.89%; P < 0.001) with synergistic effect of agitation speed significantly contributing 81.03%. Taguchi design established optimal settings of investigated parameters that produced significant improvement on diesel-oil removal by consortium. This can be used to design novel bioremediation strategy that can achieve optimal decontamination of oil pollution in shorter time.

Complete Genome Sequence of Pseudomonas balearica Strain EC28, an Iron-Oxidizing Bacterium Isolated from Corroded Steel

Pseudomonas balearica strain EC28 is an iron-oxidizing bacterium isolated from corroded steel at a floating production storage and offloading facility in Australia. Here, we report its complete genome sequence, which comprises 4,642,566 bp with a GC content of 64.43%. The genome harbors 4,164 predicted protein-encoding genes.

Nitrogen Removal Performance and Metabolic Pathways Analysis of a Novel Aerobic Denitrifying Halotolerant Pseudomonas balearica Strain RAD-17

An aerobic denitrification strain, Pseudomonas balearica RAD-17, was identified and showed efficient inorganic nitrogen removal ability. The average NO3−-N, NO2−-N, and total ammonium nitrogen (TAN) removal rate (>95% removal efficiency) in a batch test was 6.22 mg/(L∙h), 6.30 mg/(L∙h), and 1.56 mg/(L∙h), respectively. Meanwhile, optimal incubate conditions were obtained through single factor experiments. For nitrogen removal pathways, the transcriptional results proved that respiratory nitrate reductases encoded by napA, which was primarily performed in aerobic denitrification and cell assimilation, were conducted by gluS and gluD genes for ammonium metabolism. In addition, adding the strain RAD-17 into actual wastewater showed obvious higher denitrification performance than in the no inoculum group (84.22% vs. 22.54%), and the maximum cell abundance achieved 28.5 ± 4.5% in a ratio of total cell numbers. Overall, the efficient nitrogen removal performance plus strong environmental fitness makes the strain RAD-17 a potential alternative for RAS (recirculating aquaculture system) effluent treatment.