An antimicrobial thiopeptide producing novel actinomycetes Streptomyces terrae sp. nov., isolated from subsurface soil of arable land.

An antimicrobial producing Gram-positive, aerobic, nonmotile, and filamentous actinobacterial strain SKN60T was isolated from soil The isolate exhibited 99.3% and 99.0% identity with Streptomyces laurentii ATCC 31255T and S. roseicoloratus TRM 44457T, respectively, in 16S rRNA gene sequence analysis. However, the genome sequence displayed maximum ANI (88.45%) and AAI (85.61%) with S. roseicoloratus TRM 44457T. Similarly, the dDDH showed 33.7% identity with S. roseicoloratus TRM 44457T. It formed a cluster with S. roseicoloratus TRM 44457T and S. laurentii ATCC 31255T in phylogenomic tree. Cell wall analysis revealed the presence of diphosphatidylglycerol, phosphatidylethanolamine, and phosphatidylcholine as major polar lipids and diaminopimelic acid as diagnostic diamino acid. Major fatty acids were iso-C15:0, anteiso-C15:0, and iso-C16:0. The G+C content was found to be 72.3 mol%. Genome sequence analysis using antiSMASH database showed occurrence of a thiopeptide biosynthesis gene cluster with 94% similarity to berninamycin from S. bernensis UC5144. The mass of 1146 Da is identical with berninamycin. But subtle differences observed in leader peptide sequence of thiopeptide and berninamycin. Notably, S. bernensis is not validly reported and thus SKN60T is the only strain containing berninamycin BGC as no other phylogenetic relative had it. Additionally, strain SKN60T differed in phenotypic and genetic characteristics with all phylogenetic relatives of the genus Streptomyces. Therefore, it is proposed as a novel species with the name Streptomyces terrae sp. nov. strain SKN60T (=MTCC 13163T; = JCM 35768T).

Description of lipase producing novel yeast species Debaryomyces apis f.a., sp. nov. and a modified pH indicator dye-based method for the screening of lipase producing microorganisms.

Four yeast strains were isolated from the gut of stingless bee, collected in Churdhar, Himachal Pradesh, India. Physiological characterization, morphological examination, and sequence analysis of small subunit ribosomal RNA (18S rRNA) genes, internal transcribed spacer (ITS) region, and D1/D2 domain of the large subunit rRNA gene revealed that the four strains isolated from the gut of stingless bee belonged to the Debaryomyces clade. Strain CIG-23HT showed sequence divergence of 7.5% from Debaryomyces nepalensis JCM 2095T, 7.8% from Debaryomyces udenii JCM 7855T, and Debaryomyces coudertii JCM 2387T in the D1/D2 domain. In the ITS region sequences, strain CIG-23HT showed a 15% sequence divergence from Debaryomyces nepalensis JCM 2095T and Debaryomyces coudertii JCM 2387T. In 18S rRNA gene sequence, the strain CIG-23HT showed 1.14% sequence divergence from Debaryomyces nepalensis JCM 2095 and and Debaryomyces coudertii JCM 2387, and 0.83% sequence divergence from Debaryomyces hansenii NRRL Y-7426. Strain CIG-23HT can utilize more carbon sources than closely related species. The findings suggest that strain CIG-23HT is a novel species of the genus Debaryomyces, and we propose to name it as Debaryomyces apis f.a., sp. nov. The holotype is CBS 16297T, and the isotypes are MTCC 12914T and KCTC 37024T. The MycoBank number of Debaryomyces apis f.a., sp. nov. is MB836065. Additionally, a method using cresol red and Bromothymol blue pH indicator dyes was developed to screen for lipase producers, which is more sensitive and efficient than the currently used phenol red and rhodamine B dye-based screening methods, and avoids the problem of less differentiable zone of hydrolysis.

Marinobacterium lacunae sp. nov. isolated from estuarine sediment.

A novel motile bacterium was isolated from a sediment sample collected in Kochi backwaters, Kerala, India. This bacterium is Gram negative, rod shaped, 1.0-1.5 µm wide, and 2.0-3.0 µm long. It was designated as strain AK27T. Colonies were grown on marine agar displayed circular, off-white, shiny, moist, translucent, flat, margin entire, 1-2 mm in diameter. The major fatty acids identified in this strain were C18:1 ω7c, C16:0, and summed in feature 3. The composition of polar lipids in the strain AK27T included phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol, one unidentified amino lipid, two unidentified aminophospholipids, two unidentified phospholipids, and six unidentified lipids. The genomic DNA of strain AK27T exhibited a G+C content of 56.4 mol%. Based on the analysis of 16S rRNA gene sequence, strain AK27T showed sequence similarity to M. ramblicola D7T and M. zhoushanense WM3T as 98.99% and 98.58%, respectively. Compared to other type strains of the Marinobacterium genus, strain AK27T exhibited sequence similarities ranging from 91.7% to 96.4%. When compared to Marinobacterium zhoushanense WM3T and Marinobacterium ramblicola D7T, strain AK27T exhibited average nucleotide identity values of 80.25% and 79.97%, and dDDH values of 22.9% and 22.6%, respectively. The genome size of the strain AK27T was 4.55 Mb, with 4,229 coding sequences. Based on the observed phenotypic and chemotaxonomic features, and the results of phylogenetic and phylogenomic analysis, this study proposes the classification of strain AK27T as a novel species within the genus Marinobacterium. The proposed name for this novel species is Marinobacterium lacunae sp. nov.

Enhancing antifungal properties of chitosan by attaching isatin-piperazine-sulfonyl-acetamide pendant groups via novel imidamide linkage.

World health organization listed fungi as priority pathogens in 2022 to counter their adverse effects on human well-being. The use of antimicrobial biopolymers is a sustainable alternative to toxic antifungal agents. In this study, we explore chitosan as an antifungal agent by grafting a novel compound N-(4-((4-((isatinyl)methyl)piperazin-1-yl)sulfonyl)phenyl) acetamide (IS). The acetimidamide linkage of IS to chitosan herein was confirmed by 13C NMR and is a new branch in chitosan pendant group chemistry. The modified chitosan films (ISCH) were studied using thermal, tensile, and spectroscopic methods. The ISCH derivatives strongly inhibit fungal pathogens of agricultural and human importance, namely Fusarium solani, Colletotrichum gloeosporioides, Myrothecium verrucaria, Penicillium oxalicum, and Candida albicans. ISCH80 showed an IC50 value of 0.85 µg/ml against M. verrucaria and ISCH100 with IC50 of 1.55 µg/ml is comparable to the commercial antifungal IC50 values of Triadiamenol (3.6 µg/ml) and Trifloxystrobin (3 µg/ml). Interestingly, the ISCH series remained non-toxic up to 2000 µg/ml against L929 mouse fibroblast cells. The ISCH series showed long-standing antifungal action, superior to our lowest observed antifungal IC50 values of plain chitosan and IS at 12.09 µg/ml and 3.14 µg/ml, respectively. ISCH films are thus suitable for fungal inhibition in an agricultural setting or food preservation.

Brevicillin, a novel lanthipeptide from the genus Brevibacillus with antimicrobial, antifungal, and antiviral activity.

AIM: This study was aimed to determine antimicrobial and antiviral activity of a novel lanthipeptide from a Brevibacillus sp. for disinfectant application. METHODS AND RESULTS: The antimicrobial peptide (AMP) was produced by a bacterial strain AF8 identified as a member of the genus Brevibacillus representing a novel species. Whole genome sequence analysis using BAGEL identified a putative complete biosynthetic gene cluster involved in lanthipeptide synthesis. The deduced amino acid sequence of lanthipeptide named as brevicillin, showed >30% similarity with epidermin. Mass determined by MALDI-MS and Q-TOF suggested posttranslational modifications like dehydration of all Ser and Thr amino acids to yield Dha and Dhb, respectively. Amino acid composition determined upon acid hydrolysis is in agreement with core peptide sequence deduced from the putative biosynthetic gene bvrAF8. Biochemical evidence along with stability features ascertained posttranslational modifications during formation of the core peptide. The peptide showed strong activity with 99% killing of pathogens at 12 µg ml-1 within 1 minute. Interestingly, it also showed potent anti-SARS-CoV-2 activity by inhibiting ∼99% virus growth at 10 µg ml-1 in cell culture-based assay. Brevicillin did not show dermal allergic reactions in BALB/c mice. CONCLUSION: This study provides detailed description of a novel lanthipeptide and demonstrates its effective antibacterial, antifungal and anti-SARS-CoV-2 activity.

Bifunctionalized nanobioprobe based rapid color-shift assay for typhoid targeting Vi capsular polysaccharide.

Typhoid fever is an acute illness caused by Salmonella Typhi and the current diagnostic gap leads to inaccurate, over-diagnosis of typhoid leading to excessive use of antibiotics. Herein, to address the challenges we describe a new rapid color-shift assay based on a novel bifunctional nanobioprobe (Vi-AgNP probe) that is functionalized with specific biomarker Vi polysaccharide and also has the co-presence of Ag as urease inhibitor. The immunoreactions between the Vi with specific antibodies (Abs) present in typhoid patient sample forms a shielding barrier over Vi-AgNP probe rendering the urease to be active, generating colored output. Vi polysaccharide coating on the AgNP was visualized using HRTEM. TEM was performed to get insight into shielding barrier formation by the Abs. MST (microscale thermophoresis) data showed less binding Kd of 7.43 µM in presence of Abs whereas probe with urease showed efficient binding with Kd 437 nM. The assay was validated using 53 human sera samples and proven effective with 100% sensitivity. The assay showed relative standard deviation (RSD) of 4.3% estimated using rabbit anti-Vi Abs. The entire procedure could be completed within 15 min. Unlike lateral flow based assays, our assay does not require multiple combination of Abs for detection. The assay format was also found compatible in paper strip test that provides promising opportunities to develop low-cost on-spot assay for clinical diagnostics.

Ion-pumping microbial rhodopsin protein classification by machine learning approach.

BACKGROUND: Rhodopsin is a seven-transmembrane protein covalently linked with retinal chromophore that absorbs photons for energy conversion and intracellular signaling in eukaryotes, bacteria, and archaea. Haloarchaeal rhodopsins are Type-I microbial rhodopsin that elicits various light-driven functions like proton pumping, chloride pumping and Phototaxis behaviour. The industrial application of Ion-pumping Haloarchaeal rhodopsins is limited by the lack of full-length rhodopsin sequence-based classifications, which play an important role in Ion-pumping activity. The well-studied Haloarchaeal rhodopsin is a proton-pumping bacteriorhodopsin that shows promising applications in optogenetics, biosensitized solar cells, security ink, data storage, artificial retinal implant and biohydrogen generation. As a result, a low-cost computational approach is required to identify Ion-pumping Haloarchaeal rhodopsin sequences and its subtype. RESULTS: This study uses a support vector machine (SVM) technique to identify these ion-pumping Haloarchaeal rhodopsin proteins. The haloarchaeal ion pumping rhodopsins viz., bacteriorhodopsin, halorhodopsin, xanthorhodopsin, sensoryrhodopsin and marine prokaryotic Ion-pumping rhodopsins like actinorhodopsin, proteorhodopsin have been utilized to develop the methods that accurately identified the ion pumping haloarchaeal and other type I microbial rhodopsins. We achieved overall maximum accuracy of 97.78%, 97.84% and 97.60%, respectively, for amino acid composition, dipeptide composition and hybrid approach on tenfold cross validation using SVM. Predictive models for each class of rhodopsin performed equally well on an independent data set. In addition to this, similar results were achieved using another machine learning technique namely random forest. Simultaneously predictive models performed equally well during five-fold cross validation. Apart from this study, we also tested the own, blank, BLAST dataset and annotated whole-genome rhodopsin sequences of PWS haloarchaeal isolates in the developed methods. The developed web server ( https://bioinfo.imtech.res.in/servers/rhodopred ) can identify the Ion Pumping Haloarchaeal rhodopsin proteins and their subtypes. We expect this web tool would be useful for rhodopsin researchers. CONCLUSION: The overall performance of the developed method results show that it accurately identifies the Ionpumping Haloarchaeal rhodopsin and their subtypes using known and unknown microbial rhodopsin sequences. We expect that this study would be useful for optogenetics, molecular biologists and rhodopsin researchers.

Metagenomics: An Approach for Unraveling the Community Structure and Functional Potential of Activated Sludge of a Common Effluent Treatment Plant.

The common effluent treatment plant (CETP) located at Baddi treats the industrial effluent from various industries, leading to the pooling of a diverse range of substrates and metabolites. The nutrient loading and its availability decide the balance of the microbial community and its diversity. The samples thus collected from the activated sludge (BS14) of CETP and Sirsa river (SR1) from the vicinity of CETP effluent discharge were processed for the whole metagenome analysis to reveal the microbial community and its functional potential. The taxonomic classification of the BS14 sample showed the dominance of the bacterial community with 96% of abundance, whereas the SR1 was populated by eukaryotes representing 50.4% of the community of SR1. The bacterial community of SR1 was constituted of 47.2%. The functional analysis of BS14 and SR1 with GhostKOALA against the KEGG database assigned 43.7% and 27.8% of the open reading frames (ORFs) with functions. It revealed the xenobiotic degradation modules with complete pathways along with resistance against the beta-lactams. The analysis with the comprehensive antibiotic resistance database (CARD) revealed 33 and 32 unique types of antimicrobial resistance in BS14 and SR1, respectively. Both the samples were dominated by the beta-lactam resistance genes. The carbohydrate-active enzyme (CAZy) database assigned a total of 6,611 and 2,941 active enzymes to BS14 and SR1, respectively. In contrast, the glycosyl hydrolases (GH) and glycosyltransferases (GT) class of enzymes were found to be abundant in both the samples as compared with polysaccharide lyases (PL), auxiliary activities (AA), carbohydrate esterases (CE), and carbohydrate-binding module (CBM).

Isolation, purification, and characterization of a novel exopolysaccharide isolated from marine bacteria Brevibacillus borstelensis M42.

Marine microbes produce polysaccharides with unique physicochemical and functional properties that help them survive in harsh marine environments. However, only a handful of marine exopolysaccharides (EPSs) have been reported to date. The present study explored the seashore of Visakhapatnam, India, to report a novel exopolysaccharide designated as Br42 produced by Brevibacillus borstelensis M42. The isolate was identified through morphological, biochemical, phylogenetic, and genome sequencing analysis. The studies on fermentation kinetics revealed that EPS Br42 was a primary metabolite with a maximum production of 1.88 ± 0.02 g/L after 60 h when production broth was fortified with 2% glucose. Additionally, EPS Br42 was found to be a heteropolysaccharide consisting of glucose and galacturonic acid with a molecular weight of about 286 kDa. Interestingly, this molecule possesses industrially relevant functional properties such as water-holding (510 ± 0.35%), oil-holding (374 ± 0.12% for coconut oil and 384 ± 0.35% for olive oil), and swelling capacities (146.6 ± 5.75%). EPS Br42 could form an emulsion that was stable at a wide pH range for about 72 h and, in fact, performed better as compared to Span 20, a commercially used synthetic emulsifier. Moreover, this EPS was also found to be heat stable and exhibited non-Newtonian pseudoplastic behavior. These physicochemical and functional properties of polysaccharides suggest that the EPS Br42 has potential for multifarious industrial applications as an emulsifier, stabilizer, viscosifier, and binding agent.

Insight Into the Beneficial Role of Lactiplantibacillus plantarum Supernatant Against Bacterial Infections, Oxidative Stress, and Wound Healing in A549 Cells and BALB/c Mice.

Lactiplantibacillus plantarum MTCC 2621 is a well-characterized probiotic strain and is reported to possess many health benefits. However, the wound healing potential of this probiotic is yet to be explored. Here, we have assessed the antibacterial, antioxidant, and wound healing activities of cell-free supernatant of Lactiplantibacillus plantarum MTCC 2621 (Lp2621). Lp2621 exhibited excellent antibacterial activity against the indicator bacteria in the agar well diffusion assay. Lp2621 did not show any hemolytic activity. The safety of Lp2621 gel was established using the skin irritation assay in BALB/c mice, and no dermal reactions were observed. The supernatant showed 60-100% protection of A549 cells against H2O2-induced stress. In the scratch assay, Lp2621 accelerated wound healing after 24 h of treatment. The percent wound healing was significantly higher in cells treated with Lp2621 at 18-24 h posttreatment. In an excision wound healing in mice, topical application of Lp2621 gel showed faster healing than the vehicle- and betadine-treated groups. Similar wound healing activity was observed in wounds infected with Staphylococcus aureus. Histological examination revealed better wound healing in Lp2621-treated mice. Topical treatment of the wounds with Lp2621 gel resulted in the upregulation of pro-inflammatory cytokine IL-6 in the early phase of wound healing and enhanced IL-10 expression in the later phase. These findings unveil a protective role of Lp2621 against bacterial infection, oxidative stress, and wound healing.

Shape-function of a novel metapyrocatechase, RW4-MPC: Metagenomics to SAXS data based insight into deciphering regulators of function.

The oxygenases have attracted considerable attention in enzyme-mediated bioremediation of xenobiotic compounds due to their high specificity, cost-effectiveness, and targeted field applications. Here, we performed a functional metagenomics approach to cope with culturability limitations to isolate a novel extradiol dioxygenase. Fosmid clone harboring dioxygenase gene was sequenced and analyzed by bioinformatics tools. One ring-cleaving dioxygenase RW4-MPC (metapyrocatechase) was purified and characterized to examine its degradation efficiency. The RW4-MPC was significantly active in the temperature and pH range of 5 to 40 °C, and 7-10, respectively, with an optimum temperature of 25 °C and pH 8. To gain insight into observed differential activity, Small-Angle X-ray Scattering (SAXS) data of the protein samples were analyzed, which brought forth that the RW4-MPC molecules form tight globular tetramers in solution. This native association was stable till 35 °C, and protein started to associate at higher temperatures, explaining heat-induced loss of function. Similarly, RW4-MPC aggregated or lost globular profile below pH 7 or at pH 10, respectively. The kinetic parameters showed the six folds high catalytic efficiency of RW4-MPC towards 2,3-dihydroxy biphenyl than catechol and its derivatives. RW4-MPC molecules showed remarkable retention of functionality in hypersaline conditions with more than 70% activity in a buffer having 3 M NaCl concentration. In concordance, SAXS data analysis showed retention of functional shape profile in hypersaline conditions. The halotolerant and oxygen insensitive nature of this enzyme makes it a potential candidate for bioremediation.

Production of Sophorolipid Biosurfactant by Insect Derived Novel Yeast Metschnikowia churdharensis f.a., sp. nov., and Its Antifungal Activity Against Plant and Human Pathogens.

Biosurfactants are potential biomolecules that have extensive utilization in cosmetics, medicines, bioremediation and processed foods. Yeast produced biosurfactants offer thermal resistance, antioxidant activity, and no risk of pathogenicity, illustrating their promising use in food formulations. The present study is aimed to assess potential of biosurfactant screened from a novel yeast and their inhibition against food spoilage fungi. A novel asexual ascomycetes yeast strain CIG-6AT producing biosurfactant, was isolated from the gut of stingless bee from Churdhar, HP, India. The phylogenetic analysis revealed that the strain CIG-6AT was closely related to Metschnikowia koreensis, showing 94.38% sequence similarity in the D1D2 region for which the name Metschnikowia churdharensis f.a., sp. nov., is proposed. The strain CIG-6AT was able to produce sophorolipid biosurfactant under optimum conditions. Sophorolipid biosurfactant from strain CIG-6AT effectively reduced the surface tension from 72.8 to 35 mN/m. Sophorolipid biosurfactant was characterized using TLC, FTIR, GC-MS and LC-MS techniques and was a mixture of both acidic and lactonic forms. Sophorolipid assessed promising activity against pathogenic fungi viz. Fusarium oxysporum (MTCC 9913), Fusarium solani (MTCC 350), and Colletotrichum gloeosporioides (MTCC 2190). The inhibitory effect of biosurfactant CIG-6AT against F. solani was studied and MIC was 49 µgm/ml, further confirmed through confocal laser scanning microscopy. We illustrated the antifungal activity of sophorolipid biosurfactant from Metschnikowia genus for the first time and suggested a novel antifungal compound against food spoilage and human fungal pathogen.

Marinobacterium alkalitolerans sp. nov., with nitrate reductase and urease activity isolated from green algal mat collected from a solar saltern.

A novel Gram-staining-negative, rod-shaped, 0.6-0.8 µm wide and 2.0-3.0 µm in length, motile bacterium designated strain AK62T, was isolated from the green algal mat collected from saltpan, Kakinada, Andhra Pradesh, India. Colonies on ZMA were circular, off-white, shiny, moist, translucent, 1-2 mm in diameter, flat, with an entire margin. The major fatty acids include C16:0, C18:1 ω7c, and summed feature 3 (C16:1 ω7c and/or C16:1 ω6c and/or iso-C14:0 3-OH). Polar lipids include diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, one unidentified aminophospholipid, three unidentified phospholipids, and one unidentified lipid. Polyamine includes Spermidine. The DNA G + C content of the strain AK62T was 58.8 mol%. Phylogenetic analysis based on 16S rRNA gene sequence revealed that strain AK62T was closely related to the type strains Marinobacterium sediminicola, Marinobacterium coralli and Marinobacterium stanieri with a pair-wise sequence similarity of 96.9, 96.6 and 96.6%, respectively, forming a distinct branch within the genus Marinobacterium and clustered with M. stanieri, M. sediminicola, M. coralli and M. maritimum cluster. Strain AK62T shares average nucleotide identity (ANIb, based on BLAST) of 78.44, 76.69, and 76.95% with M. sediminicola CGMCC 1.7287T, M. stanieri DSM 7027T, and Marinobacterium halophilum Mano11T respectively. Based on the observed phenotypic, chemotaxonomic characteristics, and phylogenetic analysis, strain AK62T is described in this study as a novel species in the genus Marinobacterium, for which the name Marinobacterium alkalitolerans sp. nov. is proposed. The type strain of M. alkalitolerans is AK62T (= MTCC 12102T = JCM 31159T = KCTC 52667T).

Taxonomically Characterized and Validated Bacterial Species Based on 16S rRNA Gene Sequences from India During the Last Decade.

Microbial taxonomy dealing with identification and characterization of prokaryotes like bacteria and archaea has always been a major area of research all over the world. Exploring diversity of microbes and description of novel species with different genes and secondary compounds is of utmost importance for better future and sustenance of life. India having an enormous range of ecosystems and diverse species inhabiting these niches is considered to be one of the richest biodiversity regions of the world. During the last decade, with newer methodologies and better technology, the prokaryotic taxonomy from India has extended our inventory of microbial communities in specific niches. However, there still exist some limitations in classifying the microbes from India as compared to that is done world-over. This review enlists the taxonomic description of novel taxa of prokaryotes from India in the past decade. A total of 378 new bacterial species have been classified from different habitats in India in the last ten years and no descriptions of archaeal species is documented till date.

Structure Elucidation and Biochemical Characterization of Environmentally Relevant Novel Extradiol Dioxygenases Discovered by a Functional Metagenomics Approach.

The release of synthetic chemical pollutants in the environment is posing serious health risks. Enzymes, including oxygenases, play a crucial role in xenobiotic degradation. In the present study, we employed a functional metagenomics approach to overcome the limitation of cultivability of microbes under standard laboratory conditions in order to isolate novel dioxygenases capable of degrading recalcitrant pollutants. Fosmid clones possessing dioxygenase activity were further sequenced, and their genes were identified using bioinformatics tools. Two positive fosmid clones, SD3 and RW1, suggested the presence of 2,3-dihydroxybiphenyl 1,2-dioxygenase (BphC-SD3) and catechol 2,3-dioxygenase (C23O-RW1), respectively. Recombinant versions of these enzymes were purified to examine their pollutant-degrading abilities. The crystal structure of BphC-SD3 was determined at 2.6-Å resolution, revealing a two-domain architecture, i.e., N-terminal and C-terminal domains, with the sequential arrangement of ßαßßß in each domain, characteristic of Fe-dependent class II type I extradiol dioxygenases. The structure also reveals the presence of conserved amino acids lining the catalytic pocket and Fe3+ metal ion in the large funnel-shaped active site in the C-terminal domain. Further studies suggest that Fe3+ bound in the BphC-SD3 active site probably imparts aerobic stability. We further demonstrate the potential application of BphC-SD3 in biosensing of catecholic compounds. The halotolerant and oxygen-resistant properties of these enzymes reported in this study make them potential candidates for bioremediation and biosensing applications.IMPORTANCE The disposal and degradation of xenobiotic compounds have been serious issues due to their recalcitrant properties. Microbial oxygenases are the fundamental enzymes involved in biodegradation that oxidize the substrate by transferring oxygen from molecular oxygen. Among oxygenases, catechol dioxygenases are more versatile in biodegradation and are well studied among the bacterial world. The use of catechol dioxygenases in the field is currently not practical due to their aerobically unstable nature. The significance of our research lies in the discovery of aerobically stable and halotolerant catechol dioxygenases that are efficient in degrading the targeted environmental pollutants and, hence, could be used as cost-effective alternatives for the treatment of hypersaline industrial effluents. Moreover, the structural determination of novel catechol dioxygenases would greatly enhance our knowledge of the function of these enzymes and facilitate directed evolution to further enhance or engineer desired properties.

Antimicrobial properties of the novel bacterial isolate Paenibacilllus sp. SMB1 from a halo-alkaline lake in India.

Antibiotic-resistance is ever growing burden on our society for the past many years. Many synthetic chemistry approaches and rational drug-design have been unable to pace up and tackle this problem. Natural resources, more specifically, the microbial diversity, on the other hand, make a traditional and still the best platform to search for new chemical scaffolds and compounds. Here, we report the antimicrobial characteristics of novel bacterial isolate from a salt lake in India. We screened the bacterial isolates for their inhibitory activity against indicator bacteria and found that four novel species were able to prevent the growth of test strains studied in vitro. Further, we characterized one novel species (SMB1T = SL4-2) using polyphasic taxonomic approaches and also purified the active ingredient from this bacterium. We successfully characterized the antimicrobial compound using mass spectroscopy and amino acid analysis. We also allocated two novel biosynthetic gene clusters for putative bacteriocins and one novel non-ribosomal peptide gene cluster in its whole genome. We concluded that the strain SMB1T belonged to the genus Paenibacilllus with the pairwise sequence similarity of 98.67% with Paenibacillus tarimensis DSM 19409T and we proposed the name Paenibacillus sambharensis sp. nov. The type strain is SMB1T (=MTCC 12884 = KCTC 33895T).

Pseudomonas koreensis Recovered From Raw Yak Milk Synthesizes a ß-Carboline Derivative With Antimicrobial Properties.

Natural evolution in microbes exposed to antibiotics causes inevitable selection of resistant mutants. This turns out to be a vicious cycle which requires the continuous discovery of new and effective antibiotics. For the last six decades, we have been relying on semisynthetic derivatives of natural products discovered in "Golden Era" from microbes, especially Streptomyces sp. Low success rates of rational drug-design sparked a resurgence in the invention of novel natural products or scaffolds from untapped or uncommon microbial niches. Therefore, in this study, we examined the microbial diversity inhabiting the yak milk for their ability to produce antimicrobial compounds. We prepared the crude fermentation extracts of fifty isolates from yak milk and screened them against indicator strains for the inhibitory activity. Later, with the aid of gel filtration chromatography followed by reversed-phase HPLC, we isolated one antimicrobial compound Y5-P1 from the strain Y5 (Pseudomonas koreensis) which showed bioactivity against Gram-positive and Gram-negative bacteria. The compound was chemically characterized using HRMS, FTIR, and NMR spectroscopy and identified as 1-acetyl-9H-ß-carboline-3-carboxylic acid. It showed minimum inhibitory activity (MIC) in the range of 62.5-250 µg /ml. The cytotoxicity results revealed that IC50 against two mammalian cell lines i.e., HepG2 and HEK293T was 500 and 750 µg/ml, respectively. This is the first report on the production of this derivative of ß-carboline by the microorganism. Also, the study enlightens the importance of microbes residing in uncommon environments or unexplored habitats in the discovery of a diverse array of natural products which could be designed further as drug candidates against highly resistant pathogens.

Virgicin, a novel lanthipeptide from Virgibacillus sp. strain AK90 exhibits inhibitory activity against Gram-positive bacteria.

There is a significant increase in the discovery of new antimicrobial compounds in recent past to combat drug resistant pathogens. Members of the genus Bacillus and related genera have been screened extensively due to their ability to produce wide range of antimicrobial compounds. In this study, we have isolated and characterized a new antimicrobial peptide from a marine bacterium identified as Virgibacillus species. The low molecular mass and stability of the antimicrobial substance pointed towards the bacteriocinogenic nature of the compound. The RAST analysis of genome sequence showed presence of a putative bacteriocin biosynthetic cluster containing genes necessary for synthesis of a lanthipeptide. Translated amino acid sequence of mature C-terminal propeptide showed identity with salivaricin A (52.2%) and lacticin A (33.3%). Accordingly, the mass (2417 Da) obtained by MALDI analysis was in agreement with posttranslational modifications of the leader peptide to yield three methyl lanthionine rings and a disulfide bond between two free cysteine residues. The lanthipeptide was named as virgicin, which selectively inhibited the growth of Gram-positive bacteria and biofilm formation by Enterococcus faecalis. Inhibition of biofilm formation by E. faecalis was also observed in in vitro model experiments using hydroxyapatite discs. Thus, virgicin appears to be a promising new bacteriocin to control oral biofilm formation by selective pathogens.

Purification, characterization and functional properties of exopolysaccharide from a novel halophilic Natronotalea sambharensis sp. nov.

An exopolysaccharide producing strain AK103T was isolated from Sambharlake, Rajasthan, India. Based on polyphasic taxonomy, the strain AK103T was found to be a novel species for which the name Natronotalea sambharensis sp. nov. is proposed. The strain was able to secrete (1.2 gL-1) EPS under optimum conditions. The FT-IR spectroscopy revealed that EPS had carboxyl, hydroxyl, carbonyl and sulfate ester groups. The high performance liquid chromatography (HPLC), gel permeation chromatography (GPC) and NMR revealed that the exopolysaccharide was composed of mannose, glucose and glucuronic acid with a molecular weight of 4.6 × 106 KDa. This novel EPS was designated as Nat-103. Interestingly, the EPS was found to have antioxidant activity and in vitro antioxidant studies showed that DPPH (2,2-diphenyl-1-picrylhydrazyl) activity increased in a dose dependent manner. Furthermore, EPS Nat-103 was able to produce gold nanoparticles which were further characterized by FT-IR, DLS and Zeta potential (ZP).

Shewanella submarina sp. nov., a gammaproteobacterium isolated from marine water.

A curved-rod-shaped bacterium was isolated from a marine (100 m depth) water sample collected from Bay of Bengal, Visakhapatnam, India. Strain NIO-S14T, was Gram-stain-negative, motile and pale-yellow. NIO-S14T was able to grow aerobically and anaerobically and could utilize a number of organic substrates. Major fatty acids were C12 : 0, iso-C13 : 0, C14 : 0, iso-C15 : 0, C16 : 0 and C16 : 1ω7c and/or C16 : 1ω6c (summed feature 3). NIO-S14T contained diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, two unidentified aminophospholipids and six unidentified lipids as polar lipids. The DNA G+C content of NIO-S14T was 47.9 mol%. The 16S rRNA gene sequence comparisons indicated that the isolate represented a member of the family Shewanellaceae within the class Gammaproteobacteria. According to the results of 16S rRNA gene sequence analysis, NIO-S14T was closely related to Shewanella coralliiwith a pair-wise sequence similarity of 99.26 %. On the basis of the sequence comparison, NIO-S14T clustered with Shewanella coralliiand together they clustered with Shewanella mangroviand seven other species of the genus Shewanella but were distantly related. DNA-DNA hybridization between NIO-S14T and Shewanella corallii DSM 21332Trevealed a relatedness of 35 %. Distinct morphological, physiological and genotypic differences from these previously described taxa supported the classification of NIO-S14T as a representative of a novel species of the genus Shewanella, for which the name Shewanellasubmarina sp. nov. is proposed. The type strain of Shewanellasubmarina is NIO-S14T (=MTCC 12524T=KCTC 52277T=LMG 30752T).