Streptomyces: connecting red-nano and grey biotechnology fields.

Anthropogenic activities are often related to the occurrence of simultaneous contaminations with heavy metals and toxic organic compounds. In addition, the increasing demand for food, clothing, and technology has increased the worldwide contamination level. Although it is not fully demonstrated, the high level of contamination in association with the indiscriminate use of antibiotics, led to the appearance of multi-resistant pathogenic microorganisms. Grey and red biotechnologies try to counteract the negative effects of pollution and antimicrobial resistance respectively. Streptomyces is well known in the field of biotechnology. In this review, we discussed the potential of these bacteria to deal with organic and inorganic pollutants and produce nanostructures with antimicrobial activity. To our knowledge, this is the first work in which a biotechnological bacterial genus such as Streptomyces is revised in two different fields of global concern, contamination, and multi-drugs resistant microorganisms.

Whole genome sequence of the multi-resistant plant growth-promoting bacteria Streptomyces sp. Z38 with potential application in agroindustry and bio-nanotechnology.

The genus Streptomyces is widely recognized for its biotechnological potential. Due to a need to improve crops, clean up the environment and produce novel antimicrobial molecules exploiting Streptomyces has become a priority. To further explore the biotechnological potential of these organisms we analyzed the genome of the strain Streptomyces sp. Z38 isolated from contaminated roots tissues. Our analysis not only confirmed the ability of the strain to produce plant growth promoting traits but also a range of mechanisms to cope with the toxic effect of heavy metals through genes involved in metal homeostasis and oxidative stress response. The production of silver nanoparticles indicated that Streptomyces sp. Z38 may find utility in Green, Grey and Red biotechnology.

Chromium(VI) reduction in Streptomyces sp. M7 mediated by a novel Old Yellow Enzyme.

Old Yellow Enzymes play key roles in several cellular processes and have become an important family of enzymes with biotechnological potential. One of the major challenges of biotechnology consists of the bioremediation of co-polluted soils with organic and inorganic compounds. In co-contaminated areas, chromium normally exists in its more toxic and carcinogenic form Cr(VI). Microorganisms can reduce this metal to the insoluble and less toxic Cr(III). Streptomyces sp. M7 is a strain able to efficiently bioremediate polluted soils with γ-hexachlorocyclohexane and Cr(VI). The complete degradation pathway for γ-hexachlorocyclohexane was recently elucidated in this strain. In the present work, we confirmed the ability of Streptomyces sp. M7 to eliminate a high percentage of Cr(VI) from a synthetic culture medium. After a transcriptional study in the presence of Cr(VI), we also report the molecular cloning of a gene coding for an Old Yellow Enzyme with chromate reductase activity. Our results suggest that the elimination of Cr(VI) by Streptomyces sp. M7 is directly related to the activity of this Old Yellow Enzyme. The importance of our work is in identifying for the first time an Old Yellow Enzyme with chromate reductase activity in Streptomyces and Actinobacteria. Finding this enzyme helps understand chromium homeostasis in Streptomyces sp. M7, in addition to opening a new research window related to Old Yellow Enzymes from Actinobacteria.

Multi-resistant plant growth-promoting actinobacteria and plant root exudates influence Cr(VI) and lindane dissipation.

The aims of this study were (1) to isolate new multi-resistant actinobacteria from soil, rhizosphere and plant samples collected from an ancient illegal pesticide storage and (2) to elucidate the effects of these microorganisms developed with maize root exudates on lindane and Cr(VI) removal. Fifty-seven phenotypically different actinobacteria were isolated and four of them, belonging to the genus Streptomyces exhibit tolerance to a mixture of lindane and Cr(VI). Two rhizospheric strains named as Streptomyces sp. Z38 and Streptomyces sp. Z2 were selected to be grown with root exudates because they showed the highest Cr(VI) and lindane removal in co-contaminated medium. When root exudates were the only carbon source, metal dissipation increased significantly either as single or mixed contaminant, compared to metal dissipation with glucose. No significant differences were found on lindane removal with root exudates or glucose, so a higher lindane concentration was evaluated. Despite of this, lindane removal remained stable while metal dissipation was notoriously lower when lindane concentration was enhanced. In addition to a good performance growing with mixed contaminants, Streptomyces strains showed plant growth promoting traits that could improve plant establishment. The results presented in this study show the importance of the screening programs addressed to find new actinobacteria able to grow in co-contaminated systems. It was also evidenced that root exudates of maize improve the growth of Streptomyces strains when they were used as carbon source, being the dissipation of Cr(VI) considerably improved in presence of lower lindane concentration.

Proteome analysis reveals differential expression of proteins involved in triacylglycerol accumulation by Rhodococcus jostii RHA1 after addition of methyl viologen.

Rhodococcus jostii RHA1 is able to degrade toxic compounds and accumulate high amounts of triacylglycerols (TAG) upon nitrogen starvation. These NADPH-dependent processes are essential for the adaptation of rhodococci to fluctuating environmental conditions. In this study, we used an MS-based, label-free and quantitative proteomic approach to better understand the integral response of R. jostii RHA1 to the presence of methyl viologen (MV) in relation to the synthesis and accumulation of TAG. The addition of MV promoted a decrease of TAG accumulation in comparison to cells cultivated under nitrogen-limiting conditions in the absence of this pro-oxidant. Proteomic analyses revealed that the abundance of key proteins of fatty acid biosynthesis, the Kennedy pathway, glyceroneogenesis and methylmalonyl-CoA pathway, among others, decreased in the presence of MV. In contrast, some proteins involved in lipolysis and ß-oxidation of fatty acids were upregulated. Some metabolic pathways linked to the synthesis of NADPH remained activated during oxidative stress as well as under nitrogen starvation conditions. Additionally, exposure to MV resulted in the activation of complete antioxidant machinery comprising superoxide dismutases, catalases, mycothiol biosynthesis, mycothione reductase and alkyl hydroperoxide reductases, among others. Our study suggests that oxidative stress response affects TAG accumulation under nitrogen-limiting conditions through programmed molecular mechanisms when both stresses occur simultaneously.

Actinobacteria: Current research and perspectives for bioremediation of pesticides and heavy metals.

Actinobacteria exhibit cosmopolitan distribution since their members are widely distributed in aquatic and terrestrial ecosystems. In the environment they play relevant ecological roles including recycling of substances, degradation of complex polymers, and production of bioactive molecules. Biotechnological potential of actinobacteria in the environment was demonstrated by their ability to remove organic and inorganic pollutants. This ability is the reason why actinobacteria have received special attention as candidates for bioremediation, which has gained importance because of the widespread release of contaminants into the environment. Among organic contaminants, pesticides are widely used for pest control, although the negative impact of these chemicals in the environmental balance is increasingly becoming apparent. Similarly, the extensive application of heavy metals in industrial processes lead to highly contaminated areas worldwide. Several studies focused in the use of actinobacteria for cleaning up the environment were performed in the last 15 years. Strategies such as bioaugmentation, biostimulation, cell immobilization, production of biosurfactants, design of defined mixed cultures and the use of plant-microbe systems were developed to enhance the capabilities of actinobacteria in bioremediation. In this review, we compiled and discussed works focused in the study of different bioremediation strategies using actinobacteria and how they contributed to the improvement of the already existing strategies. In addition, we discuss the importance of omic studies to elucidate mechanisms and regulations that bacteria use to cope with pollutant toxicity, since they are still little known in actinobacteria. A brief account of sources and harmful effects of pesticides and heavy metals is also given.

Label-free and redox proteomic analyses of the triacylglycerol-accumulating Rhodococcus jostii RHA1.

The bacterium Rhodococcus jostii RHA1 synthesizes large amounts of triacylglycerols (TAGs) under conditions of nitrogen starvation. To better understand the molecular mechanisms behind this process, we performed proteomic studies in this oleaginous bacterium. Upon nitrogen starvation, we observed a re-routing of the carbon flux towards the formation of TAGs. Under these conditions, the cellular lipid content made up more than half of the cell's dry weight. On the proteome level, this coincided with a shift towards non-glycolytic carbohydrate-metabolizing pathways. These pathways (Entner-Doudoroff and pentose-phosphate shunt) contribute NADPH and precursors of glycerol 3-phosphate and acetyl-CoA to lipogenesis. The expression of proteins involved in the degradation of branched-chain amino acids and the methylmalonyl-CoA pathway probably provided propionyl-CoA for the biosynthesis of odd-numbered fatty acids, which make up almost 30 % of RHA1 fatty acid composition. Additionally, lipolytic and glycerol-degrading enzymes increased in abundance, suggesting a dynamic cycling of cellular lipids. Conversely, abundance of proteins involved in consuming intermediates of lipogenesis decreased. Furthermore, we identified another level of lipogenesis regulation through redox-mediated thiol modification in R. jostii. Enzymes affected included acetyl-CoA carboxylase and a ß-ketoacyl-[acyl-carrier protein] synthase II (FabF). An integrative metabolic model for the oleaginous RHA1 strain is proposed on the basis of our results.

Current biotechnological applications of the genus Amycolatopsis.

Recently there has been increasing interest in possible biotechnological applications of the bacterial genus Amycolatopsis. This genus originally attracted attention for its antibiotic producing capabilities; although it is actually a multifaceted genus and a more diverse range of studies involving biotechnological processes have now been undertaken. Several works have demonstrated that the versatility shown by these bacteria is valuable in industrial applications. Here, we provide a condensed overview of the most important biotechnological applications such as bioremediation, biodegradation and bioconversion, as well as aspects that need to be explored further in order to gain a fuller insight into this genus, including its possible potential in the production of biofuel. Antibiotic production is not discussed since this is well covered by the latest edition of Bergey's Manual of Systematic Bacteriology. To our knowledge this is the first report highlighting the versatility and biotechnological potential of the genus Amycolatopsis.

Unraveling the Amycolatopsis tucumanensis copper-resistome.

Heavy metal pollution is widespread causing serious ecological problems in many parts of the world; especially in developing countries where a budget for remediation technology is not affordable. Therefore, screening for microbes with high accumulation capacities and studying their stable resistance characteristics is advisable to define cost-effective any remediation strategies. Herein, the copper-resistome of the novel copper-resistant strain Amycolatopsis tucumanensis was studied using several approaches. Two dimensional gel electrophoresis revealed that proteins of the central metabolism, energy production, transcriptional regulators, two-component system, antioxidants and protective metabolites increased their abundance upon copper-stress conditions. Transcriptome analysis revealed that in presence of copper, superoxide dismutase, alkyl hydroperoxide reductase and mycothiol reductase genes were markedly induced in expression. The oxidative damage of protein and lipid from A. tucumanensis was negligible compared with that observed in the copper-sensitive strain Amycolatopsis eurytherma. Thus, we provide evidence that A. tucumamensis shows a high adaptation towards copper, the sum of which is proposed as the copper-resistome. This adaptation allows the strain to accumulate copper and survive this stress; besides, it constitutes the first report in which the copper-resistome of a strain of the genus Amycolatopsis with bioremediation potential has been evaluated.

Responses of environmental Amycolatopsis strains to copper stress.

Copper is a redox-active metal, which acts as a catalyst in the formation of Reactive Oxygen Species (ROS) encouraging oxidative stress. Protection against oxidants is intrinsic to every living cell; however, in stress conditions, cells are forced to increase and expand their antioxidative network. In this work, the novel copper-resistant strain Amycolatopsis tucumanensis and the copper-sensitive Amycolatopsis eurytherma were grown under copper increasing concentrations in order to elucidate the dissimilar effects of the metal on the strains viability, mainly on morphology and antioxidant capacity. Although biosorbed copper encouraged ROS production in a dose-dependent manner in both strains, the increase in ROS production from the basal level to the stress conditions in A. tucumanensis is lesser than in the copper-sensitive strain; likewise, in presence of copper A. eurytherma suffered inexorable morphological alteration while A. tucumanensis was not affected. The levels of antioxidant enzymes and metallothioneins (MT) were all greater in A. tucumanensis than in A. eurytherma; in addition MT levels as well as superoxide dismutase and thioredoxin reductase activities in A. tucumanensis, were higher as higher the concentration of copper in the culture medium. This work has given evidence that an efficient antioxidant defense system might aid microorganisms to survive in copper-stress conditions; besides it constitutes the first report of oxidative stress study in the genus Amycolatopsis and contributes to enlarge the knowledge on the copper-resistance mechanisms of A. tucumanensis.