Environmental pollutions are the most significant problem worldwide. Rhodococcus sp. has a high potential for the production of secondary metabolites and degradation activity. This study aims to screen and characterize biodegradable Rhodococcus from Iranian ecosystems. The Rhodococcus isolates were recovered from 90 environmental samples and identified using conventional and molecular methods. The growth rate in the presence of pollutants and chromatography (high‐performance liquid chromatography [HPLC]) was used to determine their biodegradation capability. A total of 13 Rhodococcus isolates were characterized from the cultured samples (14.5%) that belonged to seven species. The prevalent species were R. erythropolis (4 isolates; 30.8%), R. atherivorans (3 isolates; 23%), R. ruber (2 isolates; 15.4), and R. zopfii, R. phenolicus, R. equi and R. rhodochrous 1 isolate each. The result showed that these isolates could degrade and consume phenol, polycyclic aromatic hydrocarbon (PAH) and sulfate sodium. Our results showed that the Rhodococcus species have significant potential for bioremediation of diverse types of pollutants. Therefore, more studies are recommended for the biodegradation activity of Rhodococcus.

Background: Polycyclic aromatic hydrocarbons (PAHs) have detrimental effects on human, ecosystem, and biodiversity. Bioremediation is an option that has been used to remediate and reduce the risk of contaminants such as PAHs. Microorganisms are readily available to screen and can be rapidly identified to be used in many extreme environmental conditions. Mycobacteria have a great potential for the production of bioactive compound, which have degradation activity. Due to this issue, and also, as there is no study conducted on the biodiversity of biodegradable Mycobacterium in Markazi province, the present study aimed to assess the isolation and identification of biodegradable Mycobacterium species from diverse Markazi province ecosystems. Methods: Mycobacterium were screened from a total of 30 soil, water, and sludge samples from the oil-polluted ecosystems of Markazi province and characterized to the genus and species level by applying molecular and conventional microbiological assay including the PCR amplification and sequence analysis of 16SrRNA and hsp65 genes. The growth rate in the presence of PAHs, turbidometry, and high performance liquid chromatography (HPLC) were used to determine their bioremediation capability. Results: In total, 6 Mycobacterium isolates (20%) were screened from 30 samples, which belonged to two species of Mycobacterium consisting of M. porcinum (4 isolates) and M. celeriflavum (2 isolates). The strains of M. porcinum and M. celeriflavum could degrade 70% and 90% of 1 mg/L PAH solution in 7 days. Conclusion: According to the results, the M. porcinum and M. celeriflavum have a significant capability to biodegrade the PAHs. Therefore, more investigations are recommended for separation and applicational use of the mycobacterium species for bioremediation of PAHs.