PGIAK1, a Heavy Metal Resistant Plasmid from an Obligate Alkaliphilic and Halotolerant Bacterium Isolated from the Antarctic Concordia Station Confined Environment

Jacques Mahillon,Suxia Guo,Paul Jaak Janssen

doi:10.1371/journal.pone.0072461

Abstract

pGIAK1 is a 38-kb plasmid originating from the obligate alkaliphilic and halotolerant Bacillaceae strain JMAK1. The strain was originally isolated from the confined environments of the Antarctic Concordia station. Analysis of the pGIAK1 38,362-bp sequence revealed that, in addition to its replication region, this plasmid contains the genetic determinants for cadmium and arsenic resistances, putative methyltransferase, tyrosine recombinase, spore coat protein and potassium transport protein, as well as several hypothetical proteins. Cloning the pGIAK1 cad operon in Bacillus cereus H3081.97 and its ars operon in Bacillus subtilis 1A280 conferred to these hosts cadmium and arsenic resistances, respectively, therefore confirming their bona fide activities. The pGIAK1 replicon region was also shown to be functional in Bacillus thuringiensis, Bacillus subtilis and Staphylococcus aureus, but was only stably maintained in B. subtilis. Finally, using an Escherichia coli - B. thuringiensis shuttle BAC vector, pGIAK1 was shown to display conjugative properties since it was able to transfer the BAC plasmid among B. thuringiensis strains.

Highlights

Organisms with optimal pH for growth in excess of pH 9 are defined as alkaliphiles [1]
In the course of the characterization of this alkaliphilic bacterium, we discovered that its genome contained at least two large plasmids (.20 kb)
The JMAK1 strain was originally isolated from a stairway step inside the Antarctic Concordia station by the method previously described by Van Houdt et al (2009) [23], except that alkaline medium was used to cultivate the bacteria

Summary

Introduction

Organisms with optimal pH for growth in excess of pH 9 are defined as alkaliphiles [1]. Alkaliphilic bacteria can be further divided into two groups: facultative and obligate alkaliphiles. The bacteria from the former group can grow well below or at pH 8, while the latter group cannot grow well below or at pH 8 [2]. Alkaliphilic bacteria are relatively frequent in confined environments [12]. Due to their ability of producing various types of valuable enzymes, such as alkaline proteases, alkaline amylases or alkaline cellulases, these bacteria have been widely investigated for their potential uses in biotechnological applications [1,13]

Methods

Results

Conclusion