Enzyme(s) responsible for tellurite reducing activity in a moderately halophilic bacterium, Salinicoccus iranensis strain QW6

Use of Microbial Consortia in Bioremediation of Metalloid Polluted Environments

Metalloids are released into the environment due to the erosion of the rocks or anthropogenic activities, causing problems for human health in different world regions. Meanwhile, microorganisms with different mechanisms to tolerate and detoxify metalloid contaminants have an essential role in reducing risks. In this review, we first define metalloids and bioremediation methods and examine the ecology and biodiversity of microorganisms in areas contaminated with these metalloids. Then we studied the genes and proteins involved in the tolerance, transport, uptake, and reduction of these metalloids. Most of these studies focused on a single metalloid and co-contamination of multiple pollutants were poorly discussed in the literature. Furthermore, microbial communication within consortia was rarely explored. Finally, we summarized the microbial relationships between microorganisms in consortia and biofilms to remove one or more contaminants. Therefore, this review article contains valuable information about microbial consortia and their mechanisms in the bioremediation of metalloids.

Impact of Tellurite on the Metabolism of Paenibacillus pabuli AL109b With Flagellin Production Explaining High Reduction Capacity

Tellurium (Te) is a metalloid with scarce and scattered abundance but with an increased interest in human activity for its uses in emerging technologies. As is seen for other metals and metalloids, the result of mining activity and improper disposal of high-tech devices will lead to niches with increased abundance of Te. This metalloid will be more available to bacteria and represent an increasing selective pressure. This environmental problem may constitute an opportunity to search for microorganisms with genetic and molecular mechanisms of microbial resistance to Te toxic anions. Organisms from Te-contaminated niches could provide tools for Te remediation and fabrication of Te-containing structures with added value. The objective of this study was to determine the ability of a high metal-resistant Paenibacillus pabuli strain ALJ109b, isolated from high metal content mining residues, to reduce tellurite ion, and to evaluate the formation of metallic tellurium by cellular reduction, isolate the protein responsible, and determine the metabolic response to tellurite during growth. P. pabuli ALJ109b demonstrated to be resistant to Te (IV) at concentrations higher than reported for its genus. It can efficiently remove soluble Te (IV) from solution, over 20% in 8 h of growth, and reduce it to elemental Te, forming monodisperse nanostructures, verified by scattering electron microscopy. Cultivation of P. pabuli ALJ109b in the presence of Te (IV) affected the general protein expression pattern, and hence the metabolism, as demonstrated by high-throughput proteomic analysis. The Te (IV)-induced metabolic shift is characterized by an activation of ROS response. Flagellin from P. pabuli ALJ109b demonstrates high Te (0) forming activity in neutral to basic conditions in a range of temperatures from 20°C to 37°C. In conclusion, the first metabolic characterization of a strain of P. pabuli response to Te (IV) reveals a highly resistant strain with a unique Te (IV) proteomic response. This strain, and its flagellin, display, all the features of potential tools for Te nanoparticle production.

Development of the first gene expression system for Salinicoccus strains with potential application in bioremediation of hypersaline wastewaters

Salinicoccus salsiraiae IM408 (=CGMCC13032) is a novel halophilic bacterium that we isolated from the saline soil of Da Gang Oilfield. It tolerates 60 g/l sodium chloride and up to 123 g/l (1.5 M) sodium acetate and has shown a potential application in bioremediation of wastewater with high salt and high chemical oxygen demand (COD). Two plasmids, pS408-1 and pS408-2, were identified in S. salsiraiae IM408, and the sequences and copy numbers of the plasmids were determined. Based on these plasmids, two shuttle vectors containing a replicon for Escherichia coli, ampicillin, and chloramphenicol resistance genes, as well as the replicon from pS408-1 or pS408-2, were constructed and named as pTCS101 and pTCS201, respectively. A suitable host strain, named S. salsiraiae PE01, was also developed from the wild-type by plasmid elimination. Using the plasmid pTCS101 as an expression vector, L-lactate dehydrogenase from Staphylococcus aureus was expressed successfully in S. salsiraiae PE01. This is the first gene expression system for the Salinicoccus genus. It has provided the potential for expression of desired proteins or for establishment of desired pathways in Salinicoccus strains, which would make these halophiles more advantageous in future biotechnological applications.