Characterization of manganese-oxidizing (MnII→MnIV) bacteria from Negev Desert rock varnish: implications in desert varnish formation

Abstract

A collection of 79 bacterial isolates was obtained by plating scrapings and swabs from five rock varnish samples of the Negev Desert, Israel. Of the bacterial isolates which were obtained, 74 were able to oxidize manganese (MnII→MnIV) under laboratory conditions. The manganese-oxidizing bacteria were characterized and identified, when possible, to genus. The predominant genera were Bacillus, Geodermatophilus, Arthrobacter, and Micrococcus. Examples of all of these genera were found from more than one rock. These same genera have been reported from manganese-rich rock varnish samples from the Sonoran and Mojave Deserts of North America; however, many of the strains (species?) from the Negev appear to be different from those of the American Southwest. A single manganese-oxidizing actinomycete was also isolated. The high percentage of manganese-oxidizing bacteria to total cultivable bacteria (83 to 100% depending upon sample) from the Negev suggests that they are involved in desert varnish formation.