ABSTRACT: Recent research indicates that the quantification of Sulfate-Reducing Bacteria (SRB) and other corrosive bacteria in biofilms is of great practical and scientific relevance. Common microbial techniques based on selective cell cultivation are of limited usefulness for both quantification and characterization of environmental populations since the used methods are time-consuming and inconvenient for field trials or express analysis. To determine the total concentration of bacteria composing the corrosive biofilms, our research team developed a new approach was developed using bioluminescent method of ATP detection. The method also was optimised to determine microorganisms number in mixed cultures. The study of kinetics of corrosive biofilm formation in artificial pilot systems of field trials were carried out. The influence of the following factors on biofilm formation was revealed: microbial content of media, presence of oil, sulfide layer on the surface and metal type. The express screening of potential biocides active in relation to corrosive biofilms and the determination of minimal concentrations of tested compounds leading to destruction of corrosive biofilms were demonstrated herein.
INTRODUCTION: Formation of the biofilm on metal surfaces is one of the key factors in the acceleration of corrosion. The exact sequence of the events in the formation of a biofilm depends on the condition of the environment and the organisms present. Microbial communities usually comprise mixed populations interacting with each other. The population of bacteria develops quickly, often within one or two weeks, and in some cases even within hours of immersion, followed by the production and accumulation of exopolymers. There are considerable advantages to microorganisms in forming consortia within the biofilm structure. Some of these advantages include: enzymatic interactions, concentration and exchange of nutrients, protection against environmental stress and toxins, resistance to being washed away, as well as and maintenance of stable conditions. Interactions within consortia are very complex, and may involve consumption or production of substances such as hydrogen, hydrogen sulfide or acids without any evidence of these interactions in the bulk water phase1. Microbial corrosion is the result of numerous interactions between various biofilm components, which take place in dynamic flux. Sulfate-reducing bacteria (SRB) are usually present in the corrosive biofilms on the surfaces of ship hulls, wastewater pipelines and oil industry equipment. The SRBs usually form complex biofilms with Heterotrophic Bacteria (HB) producing organic acids necessary as substrates for SRB2 . The high concentrations of SRB provoke a quick development in metal corrosion. Thereupon, the quantification of SRB and other corrosive cells in sediments, wastewaters. Common microbial techniques based on selective cell cultivation have been found to be of limited usefulness for quantification and characterization of environmental populations since the used methods are time-consuming and inconvenient for field trials or express analysis. Methods based on the application of bioluminescent method of intracellular ATP determination have been shown to be useful as alternative approach to the cell enumeration3. This paper describes a new complex method for the investigation of corrosive biofilms. To determine the total concentration of bacteria composing the corrosive biofilms.