The rising antibiotic resistance of bacteria imposes a severe threat on human health. Inhibition of bacterial virulence is an alternative approach to develop new antimicrobials. Molecules targeting antibiotic resistant enzymes have been used in combination with cognate antibiotics. It might be ideal that a molecule can simultaneously suppress virulence factors and antibiotic resistance. Here we combined genetic and computer-aided inhibitor screening to search for such molecules against the bacterial pathogen Pseudomonas aeruginosa. To identify target proteins that control both virulence and antibiotic resistance, we screened for mutants with defective cytotoxicity and biofilm formation from 93 transposon insertion mutants previously reported with increased antibiotic susceptibility. A pyrD mutant displayed defects in cytotoxicity, biofilm formation, quorum sensing and virulence in an acute mouse pneumonia model. Next, we employed a computer-aided screening to identify potential inhibitors of the PyrD protein, a dihydroorotate dehydrogenase (DHODase) involved in pyrimidine biosynthesis. One of the predicted inhibitors was able to suppress the enzymatic activity of PyrD as well as bacterial cytotoxicity, biofilm formation and antibiotic resistance. A single administration of the compound reduced the bacterial colonization in the acute mouse pneumonia model. Therefore, we have developed a strategy to identify novel treatment targets and antimicrobial molecules.

Atrazine is an s-triazine herbicide that has been used widely over 50 years. This has resulted in the contamination of surface water, groundwater and soil. For the bioremediation of atrazine-contaminated environments, we investigated the biodegradation of atrazine and bioremediation of atrazine-contaminated soil by two groups of mixed bacteria (Pseudomonas sp. ADP and Arthrobacter aurescens TC1; Arthrobacter sp. AD30 and Pseudomonas sp. AD39) and a bacterial consortium. The biodegradation experiments indicated that after the minimal medium containing 300 mg/L atrazine as nitrogen source and 3000 mg/L sucrose as carbon source were inoculated with the above-mentioned two groups of mixed bacteria and bacterial consortium and incubated at 30 with shaking for 48 h, atrazine were removed by 80% (ADP+TC1), 97% (AD30+AD39), and 96% (bacterial consortium), respectively. The bacterial consortium and the mixed bacteria containing Arthrobacter sp. AD30 and Pseudomonas sp. AD39 exhibited higher atrazine biodegradation activities. A bioremediation trial of atrazine-contaminated soil by the bacterial consortium and mixed bacteria containing AD30 and AD39 have indicated that after incubating for 15 d at 30 atrazine contained in soil (100 mg/kg) were completely removed. These results indicated that the bacterial consortium and the mixed bacteria containing AD30 and AD39 are good candidates for use in bioremediation of atrazine-contaminated soil.