Abstract
Abstract At present, the restoration of oil-contaminated lands in arid regions is becoming increasingly relevant and represents one of the key research priorities for scientists in the southern region of Kazakhstan. Addressing the challenges posed by anthropogenic and technogenic impacts on natural ecosystems is an important scientific direction in the region. In this context, a number of researchers are actively engaged in soil microbiology studies aimed at developing innovative approaches and methods that facilitate the successful rehabilitation of disturbed or degraded natural resources. Microbial remediation is a promising technology for the treatment of environmental pollution caused by oil and petroleum products, based on the metabolic potential of microorganisms. Aim of the study: To investigate the remediation process and assess the effect of different petroleum hydrocarbons on the distribution of hydrocarbon-oxidizing and nitrogen-fixing microorganisms. The distribution of hydrocarbon-oxidizing and nitrogen-fixing microorganisms depends on the level and type of soil contamination with petroleum hydrocarbons. Soil contamination with heavy (dark) petroleum fractions leads to a decrease in the abundance of all analyzed groups of microorganisms, whereas the introduction of light petroleum fractions causes a sharp increase in microbial population. It was also established that a bioremediation method using a microbial consortium composed of hydrocarbon-oxidizing and nitrogen-fixing microorganisms, combined with the additional application of 1% mannitol, enhances the efficiency of oil-contaminated soil remediation.