Identification by molecular techniques of halophilic bacteria producing important enzymes from pristine area in Campeche, Mexico

Isla Arena is located in the coordinate 20° 70´ N - 90° 45´ W, from Campeche, Mexico. In these estuaries, the ocean mixes with fresh water, and ecosystems are concentrated where petenes and pink flamingos proliferate. Crustaceans and mollusks abound in the sea. Despite its enormous marine wealth, there are no studies carried out on which halophilic microorganisms are present in these waters. In this work, the diversity and structure of the microbial community was investigated through a metagenomics approach and corroborated for sequencing of 16S rRNA genes. It was found that the phylum Fimicutes predominates with more than 50%, in almost the same proportion of the class Bacilli and with almost 41% of relative abundance of the order Bacillales. The sequencing results showed that one of the samples presented a high percentage of similarity (99.75%) using the Nucleotide BLAST program with a peculiar microorganism: Bacillus subtilis. This microorganism is one of the best characterized bacteria among the gram-positive ones. Our results demonstrate that B. subtilis can be an efficient source of proteases, lipases and cellulases, from halophilic microbial communities located in poorly explored areas.

Production, characterization, and antitumor efficiency of l-glutaminase from halophilic bacteria

Background Halophiles are an excellent source of enzymes that are not only salt stable, but also can withstand and carry out reaction efficiently under extreme conditions. l-glutaminase has attracted much attention with respect to proposed applications in several fields such as pharmaceuticals and food industries. The aim of the present study was to investigate the anticancer activity of l-glutaminase produced by halophilic bacteria. Various halophilic bacterial strains were screened for extracellular l-glutaminase production. An attempt was made to study the optimization, purification, and characterization of l-glutaminase from Bacillus sp. DV2-37. The antitumor activity of the produced enzyme was also investigated. Results The potentiality of 15 halophilic bacterial strains isolated from the marine environment that produced extracellular l-glutaminase was investigated. Bacillus sp. DV2-37 was selected as the most potent strain and optimized for enzyme production. The optimization of fermentation process revealed that the highest enzyme activity (47.12 U/ml) was observed in a medium supplemented with 1% (w/v) glucose as a carbon source, 1% (w/v) peptone as a nitrogen source, 5% (w/v) NaCl, the initial pH was 7.0, at 37 °C, using 20% (v/v) inoculum size after 96 h of incubation. The produced crude enzyme was partially purified by ammonium sulfate precipitation and dialysis. Of the various parameters tested, pH 7, 40 °C, and 5% NaCl were found to be the best for l-glutaminase activity. The enzyme also exhibited high salt and temperature stability. The antitumor effect against human breast (MCF-7), hepatocellular (HepG-2), and colon (HCT-116) carcinoma cell lines revealed that l-glutaminase produced by Bacillus sp. DV2-37 showed potent cytotoxic activity of all the tested cell lines in a dose-dependent manner with an IC50 value of 3.5, 3.4, and 3.8 µg/ml, respectively. Conclusions The present study proved that l-glutaminase produced by marine bacteria holds proper features and it has a high potential to be useful for many therapeutic applications.

Towards the Biobeneficiation of PGMs: Reviewing the Opportunities

Conventional beneficiation of the Platinum Group of Metals (PGMs) relies on the use of inorganic chemicals. With the depreciation of high grade deposits, these conventional processes are becoming less economically viable. Furthermore, the use of chemicals has serious negative impacts on the environment. To address the challenges of conventional PGM beneficiation, biobeneficiation has been proposed. In conventional flotation, the flotation behavior of the associated sulphides determines overall PGM recovery. The same principle may also be applied for the bio-beneficiation of PGMs. Therefore, this paper discusses the biobeneficiation behavior of sulphides closely associated with PGMs with the aim of postulating the bio-beneficiation behavior of PGMs associated with the same base metal sulphides. Conventional PGM processes are briefly discussed, as bio-beneficiation of PGMs is governed by similar underlying principles. Potential microorganisms for the biobeneficiation of PGMs are highlighted, as well as the corresponding conditions for their effectiveness. The use of both single cultures and mixed cultures is discussed. Depending on conditions, PGMs associated with pyrite and/or chalcopyrite were projected to be biofloatable with B. polymyxa, P. polymyxa, A. ferrooxidans, L. ferrooxidans, B. pumilus, B. subtilis, halophilic bacteria, Alicyclobacillus ferrooxidans, sulphate reducing bacteria, and mixed cultures of A. ferrooxidans, A. thiooxidans and L. ferrooxidans. Pyrite-associated PGMsare expected to be generally prone to biodepression, whereas chalcopyrite-associated PGMs are expected to be generally recovered as the floatable phase. Sulphate-reducing bacteria were reported to have a dual role on the bioflotation of sulphide ores (flotation and depression), depending on the conditions. Therefore, this type of microorganism may serve as both a depressant or a collector in the recovery of PGMs. Based on the bioflotation response of pyrrhotite to L. ferrooxidans, it is anticipated that pyrrhotite-associated PGMS can be biodepressed using L. ferrooxidans. In terms of bioflocculation, PGMs associated with chalcopyrite may be recovered using L. ferrooxidans, whereas A. ferrooxidans, A. thiooxidans, B. polyxyma and B. subtilis can be used in the bioflocculation of pyrite-associated PGMs. M. phlei can be employed in the reverse bioflocculation of pyrite-associated PGMs. Although no information was found on the biobeneficiation of pentlandite, postulations were made based on other sulphide minerals. It was postulated that biobeneficiation (biodepression and bioflotation) with pentlandite-associated PGMs should be possible using A. ferrooxidans. It is also projected that sulphate-reducing bacteria will be suitable for the bioflotation of PGMs associated with pentlandite. The removal of gangue species such as silicates and chromites associated with PGM concentrates was also discussed. A. ferrooxidans, P. polymyxa and B. mucilaginous are candidates for the removal of gangue species. Furthermore, the need to control process conditions was highlighted. The most suitable conditions for biobeneficiation of the various base metal sulphide minerals associated with PGMs are presented in the paper. Most of the challenges associated with biobeneficiation of PGMs are already common to conventional methods, and the means of circumventing them are already well established. Developments in genetic engineering and the advent of new data science techniques are tools that could make the biobeneficiation of PGMs a possibility.

Net Charges of the Ribosomal Proteins of the S10 and spc Clusters of Halophiles Are Inversely Related to the Degree of Halotolerance

The net charges (at pH 7.4) of the ribosomal proteins (r-proteins) that comprise the S10-spc cluster show an inverse relationship with the halophilicity/halotolerance levels in both bacteria and archaea. In non-halophilic bacteria, the S10-spc cluster r-proteins are generally basic (positively charged), while the rest of the proteomes in these strains are generally acidic.

Characterization of Planococcus dechangensis isolated from a water sample of Çamaltı Saltern

In the present study, strain MHDS3 was isolated from a water sample of Çamaltı Saltern and identified using conventional and molecular methods. 16S rRNA gene sequence analyses showed that the strain MHDS3 belonged to Planococcus dechangensis species. It gave a positive result in the Gram staining test. The cells were coccus, non-motile, aerobic, catalase positive, oxidase negative and the colony pigmentation was yellow-orange. It showed negative results for citrate utilization, indole production from tryptophane, Voges-Proskauer and methyl red. This isolate was able to grow at 10-45°C (optimally 35°C), pH 6-8 (optimally pH 7) and 3-20% NaCl (optimally 10% NaCl). It was not able to grow at 4°C, 10°C, 50°C, salt-free, 0.5%, 25%, %30 total salt, pH 4-5, and pH 9-12. Glucose, ribose, fructose, sucrose, maltose were used by the test isolate as carbon sources. Different amino acids found in the structure of animal hide such as L-lysine, L-arginine, L-cysteine, L-alanine, L-tyrosine, L-histidine were also utilized by the bacterium. During the salt production process, this bacterium may contaminate the salt which is used in the food and leather industries. The activities of harmful moderately halophilic bacteria should be prevented by effective antimicrobial applications.

Net charges of the ribosomal proteins of the S10 and spc clusters of halophiles are inversely related to the degree of halotolerance

Net positive charge(s) on ribosomal proteins (r-proteins) have been reported to influence the assembly and folding of ribosomes. A high percentage of r-proteins from extremely halophilic archaea are known to be acidic or even negatively charged. Those proteins that remain positively charged are typically far less so. Herein the analysis is extended to the non-archaeal halophilic bacteria, eukaryotes and halotolerant archaea. The net charges (pH 7.4) of r-proteins that comprise the S10-spc operon/cluster from individual microbial and eukaryotic genomes were estimated and intercompared. It was observed that as a general rule, as the salt tolerance of the bacterial strains increased from 5 to 15%, the net charges of the individual proteins remained mostly basic. The most striking exceptions were the extremely halophilic bacterial strains, Salinibacter ruber SD01, Acetohalobium arabaticum DSM 5501 and Selenihalanaerobacter shriftii ATCC BAA-73, which are reported to require a minimum of 18%-21% of salt for their growth. All three strains have a higher number of acidic S10-spc cluster r-proteins than what is seen in the moderate halophiles or the halotolerant strains. Of the individual proteins, only uL2 never became acidic. uS14 and uL16 also seldom became acidic. The net negative charges on several of the S10-spc cluster r-proteins is a feature generally shared by all extremely halophilic archaea and bacteria. The S10-spc cluster r-proteins of halophilic fungi and algae (eukaryotes) were exceptions. They were positively charged despite the halophilicity of the organisms.