Methylobacterium strains were isolated from mangrove samples collected in Bertioga, SP, Brazil, from locations either contaminated or uncontaminated by oil spills. The tolerances of the strains to different heavy metals were assessed by exposing them to different concentrations of cadmium, lead, and arsenic (0.1？mM, 0.5？mM, 1？mM, 2？mM, 4？mM, and 8？mM). Additionally, the genetic diversity of Methylobacterium spp. was determined by sequence analysis of the 16S rRNA genes. The isolates from the contaminated locations were grouped, suggesting that oil can select for microorganisms that tolerate oil components and can change the methylotrophic bacterial community. Cadmium is the most toxic heavy metal assessed in this work, followed by arsenic and lead, and two isolates of Methylobacterium were found to be tolerant to all three metals. These isolates have the potential to bioremediate mangrove environments contaminated by oil spills by immobilizing the heavy metals present in the oil. 1. Introduction Mangrove ecosystems are widely distributed, covering approximately from 60 to 75% of the world’s coasts. These ecosystems are very important due to their great diversity of animals, plants, and microorganisms, and because they are some of the most productive environments in the world [1]. This diversity demands a high nutrient availability at the beginning of the trophic chain, conferring a high importance on the activities of microorganisms, such as bacteria, that are responsible for the processes of degradation and formation of essential compounds and for most of the carbon flow in the sediments of the mangrove forest [1]. The description and the distribution of the bacterial diversity in a mangrove forest allow for a better understanding of bacterial functions and their interactions in this ecosystem. The adaptation of bacterial species to mangrove conditions indicates a potential source of biotechnological resources to be explored, including the discovery of new bacterial species that produce enzymes that can be used for human life, agriculture, or industry [2]. The bacteria of the Methylobacterium genus belong to a subclass α-Proteobacteria that are able to degrade one-carbon compounds (C1) such as methanol and methylamine. Members of this genus are widely distributed in the environment, colonizing air, soil, sediment, water, plant nodules and grains (endophytically), and leaf surfaces (epiphytically) [3, 4]. M. extorquens is able to produce polyhydroxybutyrate (PHB) from methanol, and this process was described as an alternative to biodegradable plastic
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