Cyclohexane, naphthalene, and diesel fuel increase oxidative stress, CYP153, sodA, and recA gene expression in Rhodococcus erythropolis

Biodegradation of oil-derived hydrocarbons by marine actinobacteria: A systematic review

The intensive use of oil and its derivatives is related to a greater frequency of accidents involving the release of pollutants that cause harmful effects on ecosystems. Actinobacteria are cosmopolitan and saprophytic microorganisms of great commercial interest, but because they are predominantly found in soil, most research into the products of this phylum's metabolism has focused on this habitat. Marine actinobacteria exhibit unique metabolic characteristics in response to extreme conditions in their habitat, which distinguishes them from terrestrial actinobacteria. This systematic review aims to describe cultivable hydrocarbonoclastic marine actinobacteria, analyze their biodegradation rates, as well as discuss their respective potential for application in bioremediation techniques and their limitations. Twenty-one actinobacteria were found to be capable of degrading one or more hydrocarbons derived from petroleum. The majority of these bacteria belonged to the genera Rhodococcus, Gordonia, Pseudonocardia, Isoptericola, Microbacterium, Citricoccus, Kocuria, Brevibacterium, and Cellulosimicrobium. The highest degradation rate was obtained by the species R. ruber, which degraded 100 % of fluorene at a concentration of 100 mg/L. On the other hand, the species Streptomyces gougerotti and Micromonospora matsumotoense were able to degrade polyethylene and use the carbon derived from it to produce polylactic acid (PLA), which represents an excellent candidate for making safely degradable bioplastics, with a view to recycling and replacing conventional petroleum-based plastics. An approach that integrates physicochemical and biological methods, and optimized growth conditions can lead to greater success in decontaminating environments. Despite the number of bacteria found in the research, this number may be significantly higher. This review provides valuable information to support further studies.

Phylogenetic and Functional Diversity of Soluble Di-Iron Monooxygenases

Monooxygenase (MO) enzymes are responsible for the oxidation of hydrocarbons and other compounds in the carbon and nitrogen cycles, are important for the biodegradation of pollutants and can act as biocatalysts for chemical manufacture. The soluble di-iron monooxygenases (SDIMOs) are of interest due to their broad substrate range, high enantioselectivity and ability to oxidise inert substrates such as methane. Here, we re-examine the phylogeny and functions of these enzymes, using recent advances in the field and expansions in sequence diversity in databases to highlight relationships between SDIMOs and revisit their classification. We discuss the impact of horizontal gene transfer on SDIMO phylogeny, the potential of SDIMOs for the biodegradation of pollutants and the importance of heterologous expression as a tool for understanding SDIMO functions and enabling their use as biocatalysts. Our analysis highlights current knowledge gaps, most notably, the unknown substrate ranges and physiological roles of enzymes that have so far only been detected via genome or metagenome sequencing. Enhanced understanding of the diversity and functions of the SDIMO enzymes will enable better prediction and management of biogeochemical processes and also enable new applications of these enzymes for biocatalysis and bioremediation.

Adaptations of Rhodococcus rhodochrous Biofilms to Oxidative Stress Induced by Copper(II) Oxide Nanoparticles

Copper(II) oxide nanoparticles (CuO NPs) are used in different industries and agriculture, thus leading to their release to the environment, which raises concerns about their ecotoxicity and biosafety. The main toxicity mechanism of nanometals is oxidative stress as a result of the formation of reactive oxygen species caused by metal ions released from nanoparticles. Bacterial biofilms are more resistant to physical and chemical factors than are planktonic cells due to the extracellular polymeric matrix (EPM), which performs a protective function. Hydrocarbon-oxidizing bacteria of the genus Rhodococcus, well-known biodegraders of toxic organic pollutants and bioremediation agents, are capable of producing biofilms, which, as we proposed, are more resistant to metal nanoparticles, while the particular adaptation mechanisms have not yet been clarified. In this study, we study the adaptation mechanisms of Rhodococcus rhodochrous IEGM 1363 biofilms to CuO NPs in a wide range of concentrations (0.001-0.1 g/L), including morphological and ultrastructural cell alterations. The results obtained on the long-term dynamics (≤72 h) and localization of EPM structural components, in particular, lipids, polysaccharides, and proteins, indicated their important role in the complex adaptive response of alkanotrophic Rhodococcus to oxidative stress caused by copper nanooxide. The observed changes in the ultrastructure and element composition included binding of CuO nanoparticles by the cell wall to prevent their penetration inside cells and intracellular accumulation of potassium, magnesium, phosphorus, and sulfur in electron-dense inclusions, which may be associated with a metabolic stress reaction. Understanding the mechanisms of interaction between nanometals and Rhodococcus biofilms will contribute to the development of biocatalysts based on immobilized bacterial cells and bioremediation methods.

Surfing in the storm: how Paraburkholderia xenovorans thrives under stress during biodegradation of toxic aromatic compounds and other stressors

The adaptive mechanisms of Burkholderiales during the catabolism of aromatic compounds and abiotic stress are crucial for their fitness and performance. The aims of this report are to review the bacterial adaptation mechanisms to aromatic compounds, oxidative stress, and environmental stressful conditions, focusing on the model aromatic-degrading Paraburkholderia xenovorans LB400, other Burkholderiales, and relevant degrading bacteria. These mechanisms include (i) the stress response during aromatic degradation, (ii) the oxidative stress response to aromatic compounds, (iii) the metabolic adaptation to oxidative stress, (iv) the osmoadaptation to saline stress, (v) the synthesis of siderophore during iron limitation, (vi) the proteostasis network, which plays a crucial role in cellular function maintenance, and (vii) the modification of cellular membranes, morphology, and bacterial lifestyle. Remarkably, we include, for the first time, novel genomic analyses on proteostasis networks, carbon metabolism modulation, and the synthesis of stress-related molecules in P. xenovorans. We analyzed these metabolic features in silico to gain insights into the adaptive strategies of P. xenovorans to challenging environmental conditions. Understanding how to enhance bacterial stress responses can lead to the selection of more robust strains capable of thriving in polluted environments, which is critical for improving biodegradation and bioremediation strategies.

De novo biosynthesis of nylon 12 monomer ω-aminododecanoic acid

Nylon 12 is valued for its exceptional properties and diverse industrial applications. Traditional chemical synthesis of nylon 12 faces significant technical challenges and environmental concerns, while bioproduction from plant-extracted decanoic acid (DDA) raises issues related to deforestation and biodiversity loss. Here, we show the development of an engineered Escherichia coli cell factory capable of biosynthesizing the nylon 12 monomer, ω-aminododecanoic acid (ω-AmDDA), from glucose. We enable de novo biosynthesis of ω-AmDDA by introducing a thioesterase specific to C12 acyl-ACP and a multi-enzyme cascade converting DDA to ω-AmDDA. Through modular pathway engineering, redesign and dimerization enhancement of the rate-limiting P450, reconstruction of redox and energy homeostasis, and enhancement of oxidative stress tolerance, we achieve a production level of 471.5 mg/L ω-AmDDA from glucose in shake flasks. This work paves the way for sustainable nylon 12 production and offers insights for bioproduction of other fatty acid-derived products.

An Active and Versatile Electron Transport System for Cytochrome P450 Monooxygenases from the Alkane Degrading Organism Acinetobacter sp. OC4

Cytochrome P450 monooxygenases (CYPs) are valuable biocatalysts for the oxyfunctionalization of non-activated carbon-hydrogen bonds. Most CYPs rely on electron transport proteins as redox partners. In this study, the ferredoxin reductase (FdR) and ferredoxin (FD) for a cytochrome P450 monooxygenase from Acinetobacter sp. OC4 are investigated. Upon heterologous production of both proteins independently in Escherichia coli, spectral analysis showed their reduction capability towards reporter electron acceptors, e. g., cytochrome c. The individual proteins' specific activity towards cytochrome c reduction was 25 U mg-1. Furthermore, the possibility to enhance electron transfer by artificial fusion of the units was elucidated. FdR and FD were linked by helical linkers [EAAAK]n, flexible glycine linkers [GGGGS]n or rigid proline linkers [EPPPP]n of n=1-4 sequence repetitions. The system with a glycine linker (n=4) reached an appreciable specific activity of 19 U mg-1 towards cytochrome c. Moreover, their ability to drive different members of the CYP153A subfamily is demonstrated. By creating artificial self-sufficient P450s with FdR, FD, and a panel of four CYP153A representatives, effective hydroxylation of n-hexane in a whole-cell system was achieved. The results indicate this protein combination to constitute a functional and versatile surrogate electron transport system for this subfamily.

Occupational Injuries and Health Status Among Rural Tribal Non-Traditional Fishing Communities in the Coastal Region of Tamil Nadu, India

OBJECTIVES

This study evaluated the occupational injuries and health hazards associated with fishing as an occupation among non-traditional rural tribal fishing communities in the coastal region of Tamil Nadu, India.

METHODS

This cross-sectional study included a total of 170 individuals belonging to a fishing community, comprising both male (n = 82) and female (n = 88) participants. The demographic details including occupational history, lifestyle characteristics, socio-economic status, personal habits, and health status were assessed through the questionnaire survey.

RESULTS

The fishing community has a low socioeconomic status and poor literacy, lifestyle, and personal habits. The mean age of the participants was 38.8 yrs (male 34.8; female 39.9 yrs). Only 10% reported usage of personal protective equipment (PPE), and the work duration varied from 8 to 24 hrs in a day. While male subjects reported smoking habits (12%) and alcohol consumption (23%), none of the females reported alcohol consumption and smoking habits. The major occupational injuries that occurred were due to catfish (72%) and oysters (48%). A large number of female subjects reported musculoskeletal pains. The body mass index of about 28% of fishermen was above the normal range. Abnormal blood sugar, blood pressure, and respiratory and neurological symptoms were the other major health complaints. The major environmental hazards reported were salinity, solar radiation, tides, and high wind.

CONCLUSION

Injuries from handling fish and oysters were observed to be the major occupational burden. Additonally, a high prevalence of musculoskeletal pain and chronic health illness was commonly observed among the fishers. Adequate training and awareness programs are required for effective management of occupational health hazards and health promotion.

Update on new trend and progress of the mechanism of polycyclic aromatic hydrocarbon biodegradation by Rhodococcus, based on the new understanding of relevant theories: a review

Rapid industrial and societal developments have led to substantial increases in the use and exploitation of petroleum, and petroleum hydrocarbon pollution has become a serious threat to human health and the environment. Polycyclic aromatic hydrocarbons (PAHs) are primary components of petroleum hydrocarbons. In recent years, microbial remediation of PAHs pollution has been regarded as the most promising and cost-effective treatment measure because of its low cost, robust efficacy, and lack of secondary pollution. Rhodococcus bacteria are regarded as one of main microorganisms that can effectively degrade PAHs because of their wide distribution, broad degradation spectrum, and network-like evolution of degradation gene clusters. In this review, we focus on the biological characteristics of Rhodococcus; current trends in PAHs degradation based on knowledge maps; and the cellular structural, biochemical, and enzymatic basis of degradation mechanisms, along with whole genome and transcriptional regulation. These research advances provide clues for the prospects of Rhodococcus-based applications in environmental protection.

The role of oxidative stress in genome destabilization and adaptive evolution of bacteria

The review is devoted to bacterial genome destabilization by oxidative stress. The article discusses the main groups of substances causing such stress. Stress regulons involved in destabilization of genetic material and mechanisms enhancing mutagenesis, bacterial genome rearrangements, and horizontal gene transfer, induced by oxidative damage to cell components are also considered. Based on the analysis of publications, it can be claimed that rapid development of new food substrates and ecological niches by microorganisms occurs due to acceleration of genetic changes induced by oxidative stress, mediated by several stress regulons (SOS, RpoS and RpoE) and under selective pressure. The authors conclude that non-lethal oxidative stress is probably-one of the fundamental processes that guide evolution of prokaryotes and a powerful universal trigger for adaptive destabilization of bacterial genome under changing environmental conditions.

Bioaccessible PAH influence on distribution of antibiotic resistance genes and soil toxicity of different types of land use

For a better understanding of the dissemination of antibiotic resistance genes (ARGs) in natural microbial communities, it is necessary to study the factors influencing it. There are not enough studies showing the connection of some pollutants with the dissemination of ARGs and especially few works on the effect of polycyclic aromatic compounds (PAHs) on the spread of resistance in microbiocenosis. In this respect, the aim of the study was to determine the effect of bioaccessible PAHs on soil resistome. The toxicity and the content of bioaccessible PAHs and ARGs were studied in 64 samples of soils of different types of land use in the Rostov Region of Russia. In most soils, a close positive correlation was demonstrated between different ARGs and bioaccessible PAHs with different content of rings in the structure. Six of the seven studied ARGs correlated with the content of 2-, 3-, 4-, 5- or 6-ring PAHs. The greatest number of close correlations was found between the content of PAHs and ARGs in the soils of protected areas, for agricultural purposes, and in soils of hospitals. The diverse composition of microbial communities in these soils might greatly facilitate this process. A close correlation between various toxic effects identified with a battery of whole-cell bacterial biosensors and bioaccessible PAHs of various compositions was established. This correlation showed possible mechanisms of PAHs' influence on microorganisms (DNA damage, oxidative stress, etc.), which led to a significant increase in horizontal gene transfer and spread of some ARGs in soil microbial communities. All this information, taken together, suggests that bioaccessible PAHs can enhance the spread of antibiotic resistance genes.

Genotoxic Effect of Dicyclopropanated 5-Vinyl-2-Norbornene

Dicyclopropanated 5-vinyl-2-norbornene (dcpVNB) is a strained polycyclic hydrocarbon compound with a high energy content, which makes it promising for the development of propellant components based on it. In this work, the genotoxic properties of dcpVNB were studied using whole-cell lux-biosensors based on Escherichia coli and Bacillus subtilis. It was shown that the addition of dcpVNB to bacterial cells leads to the appearance of DNA damage inducing the SOS response and Dps expression with slight activation of the OxyR-mediated response to oxidative stress. The highest toxic effect of dcpVNB is detected by the following lux-biosensors: E. coli pColD-lux, E. coli pDps, B. subtilis pNK-DinC, and B. subtilis pNK-MrgA, in which the genes of bacterial luciferases are transcriptionally fused to the corresponding promoters: P_cda, P_dps, P_dinC, and P_mrgA. It was shown that lux-biosensors based on B. subtilis, and E. coli are almost equally sensitive to dcpVNB, which indicates the same permeability to this compound of cell wall of Gram-positive and Gram-negative bacteria. The activation of P_dps after dcpVNB addition maintains even in oxyR mutant E. coli strains, which means that the P_dps induction is only partially determined by the OxyR/S regulon. Comparison of specific stress effects caused by dcpVNB and 2-ethyl(bicyclo[2.2.1]heptane) (EBH), characterized by the absence of cyclopropanated groups, shows that structural changes in hydrocarbons could significantly change the mode of toxicity.

Groups of Geomicrobiological Indicators Are Spread across Gas-Hydrate and Non-Gas-Hydrate Areas in the Northern Part of the Sea of Japan

The bioindication of oil and gas fields is a field of geomicrobiology that is mainly devoted to the detection of hydrocarbon-oxidizing microbial indicator species or functional genes in total DNA. However, it appears promising to use the physiological properties of microorganisms detection deposit type of hydrocarbons, in particular their ability to oxidize hydrocarbons under aerobic and anaerobic conditions. In this study, the most promising approach in this area was the method used for assessing the anaerobic degradation of hydrocarbons. When comparing molecular genetics and cultured methods of bioindication, it can be concluded that molecular biomarkers of functional genes for the anaerobic destruction of hydrocarbons (masD) make it possible to separate areas with traditional and gas-hydrate types of deposits. Using cultured methods, we found that representatives of the Nocardiaceae family of the phylum Actinomycetota were tied to the areas where gas hydrates were found. The ability of aerobic and facultative anaerobic hydrocarbon-oxidizing microorganisms to anaerobically utilize hydrocarbons was determined with cultured methods. For the first time, this ability was revealed for the genera Stenotrophomonas, Psychrobacter, Micrococcus and Peribacillus. The wide distribution of this ability that we found in strains isolated from both study regions suggests its prominent role in the destruction of hydrocarbons in marine sediments.

A mechanistic understanding of polyethylene biodegradation by the marine bacterium Alcanivorax

Polyethylene (PE) is one of the most recalcitrant carbon-based synthetic materials produced and, currently, the most ubiquitous plastic pollutant found in nature. Over time, combined abiotic and biotic processes are thought to eventually breakdown PE. Despite limited evidence of biological PE degradation and speculation that hydrocarbon-degrading bacteria found within the plastisphere is an indication of biodegradation, there is no clear mechanistic understanding of the process. Here, using high-throughput proteomics, we investigated the molecular processes that take place in the hydrocarbon-degrading marine bacterium Alcanivorax sp. 24 when grown in the presence of low density PE (LDPE). As well as efficiently utilising and assimilating the leachate of weathered LDPE, the bacterium was able to reduce the molecular weight distribution (M_w from 122 to 83 kg/mol) and overall mass of pristine LDPE films (0.9 % after 34 days of incubation). Most interestingly, Alcanivorax acquired the isotopic signature of the pristine plastic and induced an extensive array of metabolic pathways for aliphatic compound degradation. Presumably, the primary biodegradation of LDPE by Alcanivorax sp. 24 is possible via the production of extracellular reactive oxygen species as observed both by the material's surface oxidation and the measurement of superoxide in the culture with LDPE. Our findings confirm that hydrocarbon-biodegrading bacteria within the plastisphere may in fact have a role in degrading PE.

Responses to Ecopollutants and Pathogenization Risks of Saprotrophic Rhodococcus Species

Under conditions of increasing environmental pollution, true saprophytes are capable of changing their survival strategies and demonstrating certain pathogenicity factors. Actinobacteria of the genus Rhodococcus, typical soil and aquatic biotope inhabitants, are characterized by high ecological plasticity and a wide range of oxidized organic substrates, including hydrocarbons and their derivatives. Their cell adaptations, such as the ability of adhering and colonizing surfaces, a complex life cycle, formation of resting cells and capsule-like structures, diauxotrophy, and a rigid cell wall, developed against the negative effects of anthropogenic pollutants are discussed and the risks of possible pathogenization of free-living saprotrophic Rhodococcus species are proposed. Due to universal adaptation features, Rhodococcus species are among the candidates, if further anthropogenic pressure increases, to move into the group of potentially pathogenic organisms with "unprofessional" parasitism, and to join an expanding list of infectious agents as facultative or occasional parasites.

Microbial Degradation of Naphthalene and Substituted Naphthalenes: Metabolic Diversity and Genomic Insight for Bioremediation

Low molecular weight polycyclic aromatic hydrocarbons (PAHs) like naphthalene and substituted naphthalenes (methylnaphthalene, naphthoic acids, 1-naphthyl N-methylcarbamate, etc.) are used in various industries and exhibit genotoxic, mutagenic, and/or carcinogenic effects on living organisms. These synthetic organic compounds (SOCs) or xenobiotics are considered as priority pollutants that pose a critical environmental and public health concern worldwide. The extent of anthropogenic activities like emissions from coal gasification, petroleum refining, motor vehicle exhaust, and agricultural applications determine the concentration, fate, and transport of these ubiquitous and recalcitrant compounds. Besides physicochemical methods for cleanup/removal, a green and eco-friendly technology like bioremediation, using microbes with the ability to degrade SOCs completely or convert to non-toxic by-products, has been a safe, cost-effective, and promising alternative. Various bacterial species from soil flora belonging to Proteobacteria (Pseudomonas, Pseudoxanthomonas, Comamonas, Burkholderia, and Novosphingobium), Firmicutes (Bacillus and Paenibacillus), and Actinobacteria (Rhodococcus and Arthrobacter) displayed the ability to degrade various SOCs. Metabolic studies, genomic and metagenomics analyses have aided our understanding of the catabolic complexity and diversity present in these simple life forms which can be further applied for efficient biodegradation. The prolonged persistence of PAHs has led to the evolution of new degradative phenotypes through horizontal gene transfer using genetic elements like plasmids, transposons, phages, genomic islands, and integrative conjugative elements. Systems biology and genetic engineering of either specific isolates or mock community (consortia) might achieve complete, rapid, and efficient bioremediation of these PAHs through synergistic actions. In this review, we highlight various metabolic routes and diversity, genetic makeup and diversity, and cellular responses/adaptations by naphthalene and substituted naphthalene-degrading bacteria. This will provide insights into the ecological aspects of field application and strain optimization for efficient bioremediation.

Stress response in Rhodococcus strains

Rhodococci are bacteria which can survive under various extreme conditions, in the presence of toxic compounds, and in other hostile habitats. Their tolerance of unfavorable conditions is associated with the structure of their cell wall and their large array of enzymes, which degrade or detoxify harmful compounds. Their physiological and biotechnological properties, together with tools for their genetic manipulation, enable us to apply them in biotransformations, biodegradation and bioremediation. Many such biotechnological applications cause stresses that positively or negatively affect their efficiency. Whereas numerous reviews on rhodococci described their enzyme activities, the optimization of degradation or production processes, and corresponding technological solutions, only a few reviews discussed some specific effects of stresses on the physiology of rhodococci and biotechnological processes. This review aims to comprehensively describe individual stress responses in Rhodococcus strains, the interconnection of different types of stresses and their consequences for cell physiology. We examine here the responses to (1) environmental stresses (desiccation, heat, cold, osmotic and pH stress), (2) the presence of stress-inducing compounds (metals, organic compounds and antibiotics) in the environment (3) starvation and (4) stresses encountered during biotechnological applications. Adaptations of the cell envelope, the formation of multicellular structures and stresses induced by the interactions of hosts with pathogenic rhodococci are also included. The roles of sigma factors of RNA polymerase in the global regulation of stress responses in rhodococci are described as well. Although the review covers a large number of stressful conditions, our intention was to provide an overview of the selected stress responses and their possible connection to biotechnological processes, not an exhaustive survey of the scientific literature. The findings on stress responses summarized in this review and the demonstration of gaps in current knowledge may motivate researchers working to fill these gaps.

Cadmium enhances conjugative plasmid transfer to a fresh water microbial community

Co-selection of antibiotic resistance genes (ARGs) by heavy metals might facilitate the spread of ARGs in the environments. Cadmium contamination is ubiquitous, while, it remains unknown the extent to which cadmium (Cd²⁺) impact plasmid-mediated transfer of ARGs in aquatic bacterial communities. In the present study, we found that Cd²⁺ amendment at sub-inhibitory concentration significantly increased conjugation frequency of RP4 plasmid from Pseudomonas putida KT2442 to a fresh water microbial community by liquid mating method. Cd²⁺ treatment (1-100 mg/L) significantly increased the cell membrane permeability and antioxidant activities of conjugation mixtures. Amendments of 10 and 100 mg/L Cd²⁺ significantly enhanced the mRNA expression levels of mating pair formation gene (trbBp) and the DNA transfer and replication gene (trfAp) due to the repression of regulatory genes (korA, korB and trbA). Phylogenetic analysis of transconjugants indicated that Proteobacteria was the dominant recipients and high concentration of Cd²⁺ treatment resulted in expanded recipient taxa. This study suggested that sub-inhibitory Cd²⁺ contamination would facilitate plasmid conjugation and contributed to the maintenance and spread of plasmid associated ARGs, and highlighted the urgent need for effective remediation of Cd²⁺ in aquatic environments.

Genotoxic effect of 2,2'-bis(bicyclo[2.2.1] heptane) on bacterial cells

The toxic effect of strained hydrocarbon 2,2'-bis (bicyclo[2.2.1]heptane) (BBH) was studied using whole-cell bacterial lux-biosensors based on Escherichia coli cells in which luciferase genes are transcriptionally fused with stress-inducible promoters. It was shown that BBH has the genotoxic effect causing bacterial SOS response however no alkylating effect has been revealed. In addition to DNA damage, there is an oxidative effect causing the response of OxyR/S and SoxR/S regulons. The most sensitive to BBH lux-biosensor was E. coli pSoxS-lux which reacts to the appearance of superoxide anion radicals in the cell. It is assumed that the oxidation of BBH leads to the generation of reactive oxygen species, which provide the main contribution to the genotoxicity of this substance.

Cyclohexane, naphthalene, and diesel fuel increase oxidative stress, CYP153, sodA, and recA gene expression in Rhodococcus erythropolis

In this study, we compared the expression of CYP153, sodA, sodC, and recA genes and ROS generation in hydrocarbon-degrading Rhodococcus erythropolis in the presence of cyclohexane, naphthalene, and diesel fuel. The expression of cytochrome P450, sodA (encoding Fe/Mn superoxide dismutase), recA, and superoxide anion radical generation rate increased after the addition of all studied hydrocarbons. The peak of CYP153, sodA, and recA gene expression was registered in the presence of naphthalene. The same substrate upregulated the Cu/Zn superoxide dismutase gene, sodC. Cyclohexane generated the highest level of superoxide anion radical production. Hydrogen peroxide accumulated in the medium enriched with diesel fuel. Taken together, hydrocarbon biotransformation leads to oxidative stress and upregulation of antioxidant enzymes and CYP153 genes, and increases DNA reparation levels in R. erythropolis cells.