Microbe- plant interaction as a sustainable tool for mopping up heavy metal contaminated sites.

BACKGROUND: Phytoremediation is a green technology that removes heavy metal (HM) contamination from the environment by using HM plant accumulators. Among soil microbiota, plant growth promoting bacteria (PGPR) have a role influencing the metal availability and uptake. METHODS: This current study evaluates the plant growth promoting qualities of microbial flora isolated from rhizosphere, plant roots, and marine aquatic HMs polluted environments in Alexandria through several biochemical and molecular traits. Metal contents in both collected soils and plant tissues were measured. Transcript levels of marker genes (HMA3 and HMA4) were analyzed. RESULTS: Three terrestrial and one aquatic site were included in this study based on the ICP-MS identification of four HMs (Zn, Cd, Cu, and Ni) or earlier reports of HMs contamination. Using the VITEK2 bacterial identification system, twenty-two bacteria isolated from these loci were biochemically described. Pseudomonas and Bacillus were the most dominant species. Furthermore, the soil microbiota collected from the most contaminated HMs site with these two were able to enhance the Helianthus annuus L. hyper-accumulation capacity significantly. Specifically, sunflower plants cultivated in soils with HMs adapted bacteria were able to accumulate about 1.7-2.5-folds more Zn and Cd in their shoots, respectively. CONCLUSION: The influence of PGPR to stimulate crop growth under stress is considered an effective strategy. Overall, our findings showed that plants cultivated in HMs contaminated sites in the presence of PGPR were able to accumulate significant amounts of HMs in several plant parts than those cultivated in soils lacking microbiota.

Suggested Sustainable Medical and Environmental Uses of Melanin Pigment From Halotolerant Black Yeast Hortaea werneckii AS1.

The marine ecosystem is a complex niche with unique environmental circumstances. Microbial communities from the sea are one of the main origins of compounds with tremendous capabilities. Marine yeasts have the ability to produce secondary metabolites that are architecturally distinct from those found in terrestrial species. Melanin pigment synthesized by marine halotolerant black yeast Hortaea werneckii AS1 isolated from Mediterranean salt lakes in Alexandria, Egypt was found to exert a radical scavenging effect on 2,2-diphenyl-1-picrylhydrazyl (DPPH) with an IC50 of 61.38 µg/ml. Furthermore, it showed no cytotoxicity toward human skin fibroblast cell line (HSF) with an IC50 value above 0.1 mg/ml. The antimicrobial capability of the pigment was revealed against the tested number of bacterial and fungal strains with the highest inhibition zone of 25 mm against Aeromonas sp. and a growth inhibition percentage up to 63.6% against Aspergillus niger. From an environmental impact point of view, the pigment disclosed a heavy metal removal efficiency of 85.7, 84.8, and 81.5% for Pb2+, Cd2+, and Ni2+, respectively, at 100 mg/L metal concentration. The previously mentioned results suggested melanin from H. werneckii AS1 as a promising biocompatible candidate in various medical, cosmetics, pharmaceutical, and environmental applications.

Optimization of melanin pigment production from the halotolerant black yeast Hortaea werneckii AS1 isolated from solar salter in Alexandria.

BACKGROUND: Melanins are one of the magnificent natural pigments synthesized by a wide range of microorganisms including different species of fungi and bacteria. Marine black yeasts appear to be potential prospects for the synthesis of natural melanin pigment. As a result, the goal of this research was to isolate a marine black yeast melanin-producing strain and improve the culturing conditions in order to maximize the yield of such a valuable pigment. RESULTS: Among five locally isolated black yeast strains, the only one that demonstrated a potent remarkable melanin pigment production was identified using ITS rDNA as Hortaea werneckii AS1. The extracted pigment's physiochemical characterization and analytical investigation with Ultraviolet-Visible (UV) spectrophotometry, Fourier Transform-Infrared spectroscopy (FTIR), and Scanning Electron Microscope (SEM) confirmed its nature as a melanin pigment. The data obtained from the polynomial model's maximum point suggested that CaCl2, 1.125 g/L; trace element, 0.25 ml/L; and a culture volume 225 mL/500 mL at their optimal values were the critical three elements impacting melanin production. In comparison with the baseline settings, the response surface methodology (RSM) optimization approach resulted in a 2.0 - fold improvement in melanin output. CONCLUSIONS: A maximum melanin yield of 0.938 g/L proved the halotolerant H. werneckii AS1 potentiality as a source for natural melanin pigment synthesis 'when compared to some relevant black yeast strains' and hence, facilitating its incorporation in a variety of pharmaceutical and environmental applications.

Polyhydroxyalkanoate nanoparticles produced by marine bacteria cultivated on cost effective Mediterranean algal hydrolysate media.

Algae are omnipresent in all seas and oceans, which make thema target for many applications such as bio-fertilizers, fish feeding and removal of heavy metals. In the present study, different algal species were examined as sustainable alternatives substrates for PHA production by Halomonas sp. Several media simulations were utilized to achieve high polymer productivity. The maximum poly(3-hydroxybutyrate) (PHB) concentrations were determined by using Corallina mediterranea hydrolysates as a carbon and nitrogen source. The isolates Halomonas pacifica ASL10 and Halomonas salifodiane ASL11 were found to be able to produce PHA by 67 % wt and 63 % wt CDW, respectively. PHB nanoparticles (NPs) had high zeta potential values and small particle sizes. These properties make it suitable for several drug delivery and pharmaceutical applications. Interestingly, NPs showed a potent antibacterial activity against several reference strains. The antibacterial efficacy of PHA-NPs has not been previously studied, thus this study opens a promising use of PHA-NPs.

Dual Therapeutic Targeting of Lung Infection and Carcinoma Using Lactoferrin-Based Green Nanomedicine.

In view of the promising applications of nanoparticles in drug delivery, this study highlights the fabrication of new bioactive green protein-polysaccharide nanocomplexes with significant antibacterial and antitumor efficacies. We preformulated the water-insoluble drugs Quercetin (Quer) and Resveratrol (Res) as water-soluble nanocrystals to facilitate their entrapment in the electrostatic lactoferrin-chondroitin (Lf-ChS) nanocomplex. Quer and Res were physically entrapped in the Lf-ChS nanomatrix with high encapsulation efficiencies (EE %) of 85.2 and 90.1% w/w for Quer and Res, respectively. The in vitro synergetic antibacterial effects of the studied compounds against all bacterial strains were confirmed. Res-Quer Lf-ChS NPs revealed an enhanced cytotoxic effect against A549 lung cancer cells. A new model of polymicrobial lung infection was designed, where treatment with Res-Quer Lf-ChS NPs (233.5 ± 6.59 nm) resulted in a marked decline of 3.2 log units in bacterial counts. In the lung tumor model, the potent antitumor efficacy of the developed Res-Quer Lf-ChS NPs was demonstrated by a noticeable decline in both lung weight and the biomarkers compared to the positive control group that did not receive any treatment. In conclusion, the green Res-Quer Lf-ChS NPs possess antibacterial and antitumor attributes for potential lung infection and tumor therapy.

Polyhydroxyalkanoates (PHA) from Halomonas pacifica ASL10 and Halomonas salifodiane ASL11 isolated from Mariout salt lakes.

Two novel PHA producing bacterial strains were chosen out of 12 strains collected from Mariout salt lakes. Analysis of 16srRNA gene sequence of the two new strains revealed 95.38% and 98.78% similarity to that of Halomonas pacifica and Halomonas salifodiane, respectively. A maximum polymer productivity of 6.9 g/l and 7.1 g/l was recorded by ASL10 and ASL11, respectively. Furthermore, a pH of 7 contributed to the highest polymer production for both strains. Interestingly, both ASL10 and ASL11showed a great ability to tolerate salinity up to 17 g/l NaCL. Moreover, both promising isolates were able to degrade crude oil efficiently by degradation percentages of 69.2% and 67.3% for ASL10 and ASL11, respectively. GCMS, FTIR, NMR, XRD and thermal properties were performed for poly (3 HV-co-3HB) characterization.

The sustainability of microbial bioplastics, production and applications.

Plastic accumulation has destructive environmental impacts, so the world needs eco-friendly plastic alternatives. Within this context, polyhydroxyalkanoates (PHAs) appear to be real alternatives to the chemical plastics because they are biocompatible and biodegradable. Despite its similar properties to common plastics, PHAs use is still hampered by higher production costs. PHAs are produced by high density fed-batch cultivation, activated sludge, microbial consortia and continuous substrate supply, and a major cost associated with their production is the carbon source used for bacterial fermentation. Therefore, novel carbon sources have been studied for PHA production including, macro algae, peanut oil, crude glycerol and whey. PHAs were applied in myriad fields such as wood production, food packaging, 3D painting, cancer detection, treating ulcers as well as several agricultural and therapeutic applications. In this review, current knowledge of methods and novel carbon sources enhance the sustainability and reliability of PHAs in the prospective future.

Genome and Proteome Analysis of Rhodococcus erythropolis MI2: Elucidation of the 4,4´-Dithiodibutyric Acid Catabolism.

Rhodococcus erythropolis MI2 has the extraordinary ability to utilize the xenobiotic 4,4´-dithiodibutyric acid (DTDB). Cleavage of DTDB by the disulfide-reductase Nox, which is the only verified enzyme involved in DTDB-degradation, raised 4-mercaptobutyric acid (4MB). 4MB could act as building block of a novel polythioester with unknown properties. To completely unravel the catabolism of DTDB, the genome of R. erythropolis MI2 was sequenced, and subsequently the proteome was analyzed. The draft genome sequence consists of approximately 7.2 Mbp with an overall G+C content of 62.25% and 6,859 predicted protein-encoding genes. The genome of strain MI2 is composed of three replicons: one chromosome and two megaplasmids with sizes of 6.45, 0.4 and 0.35 Mbp, respectively. When cells of strain MI2 were cultivated with DTDB as sole carbon source and compared to cells grown with succinate, several interesting proteins with significantly higher expression levels were identified using 2D-PAGE and MALDI-TOF mass spectrometry. A putative luciferase-like monooxygenase-class F420-dependent oxidoreductase (RERY_05640), which is encoded by one of the 126 monooxygenase-encoding genes of the MI2-genome, showed a 3-fold increased expression level. This monooxygenase could oxidize the intermediate 4MB into 4-oxo-4-sulfanylbutyric acid. Next, a desulfurization step, which forms succinic acid and volatile hydrogen sulfide, is proposed. One gene coding for a putative desulfhydrase (RERY_06500) was identified in the genome of strain MI2. However, the gene product was not recognized in the proteome analyses. But, a significant expression level with a ratio of up to 7.3 was determined for a putative sulfide:quinone oxidoreductase (RERY_02710), which could also be involved in the abstraction of the sulfur group. As response to the toxicity of the intermediates, several stress response proteins were strongly expressed, including a superoxide dismutase (RERY_05600) and an osmotically induced protein (RERY_02670). Accordingly, novel insights in the catabolic pathway of DTDB were gained.

Biodegradation of the organic disulfide 4,4'-dithiodibutyric acid by Rhodococcus spp.

Four Rhodococcus spp. exhibited the ability to use 4,4'-dithiodibutyric acid (DTDB) as a sole carbon source for growth. The most important step for the production of a novel polythioester (PTE) using DTDB as a precursor substrate is the initial cleavage of DTDB. Thus, identification of the enzyme responsible for this step was mandatory. Because Rhodococcus erythropolis strain MI2 serves as a model organism for elucidation of the biodegradation of DTDB, it was used to identify the genes encoding the enzymes involved in DTDB utilization. To identify these genes, transposon mutagenesis of R. erythropolis MI2 was carried out using transposon pTNR-TA. Among 3,261 mutants screened, 8 showed no growth with DTDB as the sole carbon source. In five mutants, the insertion locus was mapped either within a gene coding for a polysaccharide deacetyltransferase, a putative ATPase, or an acetyl coenzyme A transferase, 1 bp upstream of a gene coding for a putative methylase, or 176 bp downstream of a gene coding for a putative kinase. In another mutant, the insertion was localized between genes encoding a putative transcriptional regulator of the TetR family (noxR) and an NADH:flavin oxidoreductase (nox). Moreover, in two other mutants, the insertion loci were mapped within a gene encoding a hypothetical protein in the vicinity of noxR and nox. The interruption mutant generated, R. erythropolis MI2 noxΩtsr, was unable to grow with DTDB as the sole carbon source. Subsequently, nox was overexpressed and purified, and its activity with DTDB was measured. The specific enzyme activity of Nox amounted to 1.2 ± 0.15 U/mg. Therefore, we propose that Nox is responsible for the initial cleavage of DTDB into 2 molecules of 4-mercaptobutyric acid (4MB).