Aislamiento y selección de bacterias oxidantes de manganeso

AINELEN PIAZZA; PACINI, V; SANGUINETTI, G; INGALINELLA, A; JORGELINA OTTADO; GOTTIG, N.

Congreso; X Congreso Argentino de Microbiología General.; 2014

Sociedad Argentina de Microbiología General.

Manganese represents the 12th most abundant element in the Earth?s crust. It can exist in 11 oxidation states ranging from ?3 to +7 with two major forms in aquatic environments: Mn (II) and Mn (IV). Changes between the two major oxidation forms occur via oxidation and reduction reactions that may be abiotic or microbially mediated. Although bacterial Mn (II) oxidation is widespread, little is known about why bacteria oxidize Mn (II) and if this process gives any advantages to the bacteria that can perform it. Aside from a requirement for oxygen and iron, as well as the observation that oxidation occurs in stationary phase, very little is known about this regulation. Identifying signals or conditions that regulate oxidation could provide some insight into the role of Mn (II) oxidation in bacterial cells. The primary objective of this study was to isolate manganese-oxidizing bacteria, and study, in a future, the physiological function of the oxidation process in these isolates. Mn-oxidizing bacteria are ubiquitous, but several works demonstrated that habitats containing high levels of Mn tend to have high numbers of these bacteria. Therefore, in order to isolate Mn-oxidizing bacteria we collected samples from a biofiltration system that enables the removal of the Mn present in underground waters by the biological oxidation of this metal. Sediments were dissolved in PBS and were plated on different solid selective media containing high MnSO4 concentrations. The isolated strains were found to oxidize MnSO4 (present in the agar) as deduced from color changes. In the absence of Mn, the colonies on the agar were whitish, in contrast, in Mn-containing cultures a shift from whitish to brownish was observed. From a total of 2080 isolates evaluated we could select 82 Mn-oxidizing strains. Oligonucleotides were designed in order to amplify specific regions of the 16S RNAs by PCR. These sequences may allow the molecular identification of each strain by phylogenetic analysis. Genome data bases will be analyzed in order to screen the presence of genes with a role in Mn-oxidation processes and a strategy to obtain mutant strains in these genes will be designed. With the aim of know the environmental grown conditions of the isolated strains, we determined the general physicochemical parameters of the waters and sediments from which the bacteria were obtained. Mn and iron concentrations were measured using Flame Atomic Absorption Spectroscopy. Total sediments, pH, electrical conductivity and oxygen concentration, were measured using procedures acceptable by Standard Methods for the Examination of Water and Wastewater (2005). This may allow us to introduce modification in the culture media in order to improve the in vitro culture conditions. This work thus will contribute to the understanding of the role of Mn (II) oxidation in the evolution of bacteria.