Genetic and Phenotypic Heterogeneity of the Nocardiopsis alba Strains of Seawater

Anti-biofilm potential of some fish probiotics, alone and in combination with antibiotics against isolated aquaculture pathogens; A preliminary data

This study aims to isolate and identify both diseased and healthy fish pathogens of Ctenopharyngodon idella, Labeo rohita and Oreochromis niloticus and assess their antibacterial and biofilm supressing activities against fish pathogens. It explores their potential to inhibit and degrade biofilms, serving as an alternative to antibiotics in aquaculture while enhancing fish health and disease resistance. Furthermore, the research endeavors to assess the biofilm degradation potential of antibiotics and probiotics, both individually and in combination. The biofilm-forming potential of pathogens was assessed both qualitatively and quantitatively using the Congo red assay, cover slip, and test tube methods. Additionally, genomic sequencing through 16S rRNA ribotyping revealed the species level identification of four pathogenic and twelve probiotic strains. Three pathogens, Staphylococcus sciuri, Pseudomonas aeruginosa, and Staphylococcus xylosus, showed significant biofilm formation at day 5, while the pathogen Niallia circulans expressed maximum biofilm formation on day 7. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of antibiotics were evaluated against pathogenic strains. Antibiotic susceptibility testing revealed significant inhibition zones. MIC and MBC values ranged from 0.10 mg/ml to 85.00 mg/ml, with the agar well and disk diffusion methods demonstrating strong inhibitory effects against the pathogenic strains. Notably, fish probiotics either alone or in combination with antibiotics exhibited significant inhibition and anti-biofouling activity across three different concentrations (1/2 MIC, 1MIC, 2XMIC). The biofilm eradication values were statistically significant (p < 0.005). The findings affirm the effectiveness of the antibiotics (ampicillin, levofloxacin, kanamycin and oxytetracycline) and probiotics (Bacullus altitudinis, Bacillus pumilus, Mammaliicoccus sciuri) employed in preventing and dispersing biofilms formed by isolated fish pathogens (S. sciuri, P. aeruginosa and N. circulans). The current study explores the use of probiotics to enhance fish immunity, reduce disease risk without promoting antibiotic resistance, and disrupt pathogenic biofilms to control infections. Unlike antibiotics, probiotics are biodegradable and eco-friendly, minimizing harm to aquatic ecosystems and beneficial microbes.

Agro-industrial Waste Utilization, Medium Optimization, and Immobilization of Economically Feasible Halo-Alkaline Protease Produced by Nocardiopsis dassonvillei Strain VCS-4

The oceanic actinobacteria have strong potential to secrete novel enzymes with unique properties useful for biotechnological applications. The Nocardiopsis dassonvillei strain VCS-4, associated with seaweed Caulerpa scalpeliformis, was a halo-alkaline protease producer. Further investigation focuses on medium optimization and the use of agro-industrial waste for economically feasible, high-yield protease production. A total of 12 experimental runs were designed using Minitab-20 software and Placket-Burman design. Among the 7 physicochemical parameters analyzed, incubation time and gelatin were detected as significant factors responsible for higher protease production. Incubation time and gelatin were further analyzed using OVATs. Optimal protease production was achieved with 2% gelatin, 0.1% yeast extract, 0.1% bacteriological peptone, 7% NaCl, pH 8, 5% inoculum, and a 7-day incubation period, resulting in a maximum protease activity (Pmax) of 363.97 U/mL, generation time of 11.9 h, specific growth rate of 0.161 g/mL/h, and protease productivity (Qp) of 61.65 U/mL/h. Moreover, utilizing groundnut cake as an agro-industrial waste led to enhanced production parameters: Pmax of 408.42 U/mL, generation time of 9.74 h, specific growth rate of 0.361 g/mL/h, and Qp of 68.07 U/mL/h. The immobilization of crude protease was achieved using Seralite SRC 120 as a support matrix resulting in 470.38 U/g immobilization, 88.20% immobilization yield, and 28.90% recovery activity. Characterization of both crude and immobilized proteases revealed optimal activity at pH 10 and 70 °C. Immobilization enhanced the shelf-life, reusability, and stability of VCS-4 protease under extreme conditions.

Important ecophysiological roles of Nocardiopsis in lignocellulose degradation during aerobic compost with humic acid addition

Improving lignocellulose degradation and organic matter conversion in agricultural and livestock wastes remains a great challenge. Here, the contribution of humic acid (HA) to lignocellulose degradation was investigated, focusing on the abundance of key microbial species and carbohydrate-active enzymes during aerobic composting. The results demonstrated that the addition of HA not only increased the complexity of the microbial network, but also enhanced the positive interaction between microorganism. The abundance of phylum Actinobacteria related to lignin degradation was significantly increased, especially genus Nocardiopsis (50.97 %), and Nocardiopsis was significantly positively correlated with HA and humus (HS) (p < 0.05). Additionally, the abundance of GH (43.45%) and AA (5.88%) enzymes and the activation of metabolic pathways of AA, carbohydrates and energy were significantly increased (p < 0.05). Remarkably, the quantity of lignocellulose-degrading genes and carbohydrate-active enzymes experienced a marked boost (p < 0.05), with the peak abundance observed in Nocardiopsis. The structural equation model revealed that the addition of HA boosted the abundance of Nocardiopsis, which in turn amplified lignocellulose degradation by up-regulating lignocellulose degradation genes and enhancing carbohydrase activity, and facilitating the conversion of HA and FA. The lignocellulose degradation experiment verified that Nocardiopsis alba exhibited good ability in the degradation of cellulose and hemicellulose. These findings provided a novel perspective on the mechanisms underlying lignocellulose degradation, and broaden the understanding of the ecophysiological role of Nocardiopsis in composting system.

Comprehensive updates on the biological features and metabolic potential of the versatile extremophilic actinomycete Nocardiopsis dassonvillei

Nocardiopsis dassonvillei prevails under harsh environmental conditions and the purpose of this review is to highlight its biological features and recent biotechnological applications. The organism prevails in salt-rich soils/marine systems and some strains endure extreme temperatures and pH. A few isolates are associated with marine organisms and others cause human diseases. Comparative genomic analysis indicates its versatility in producing biotechnologically relevant metabolites. Antimicrobial, cytotoxic, anticancer and growth promoting biomolecules are obtained from this organism. It also synthesizes biotechnologically important enzymes. Bioactive compounds and enzymes obtained from this actinomycete provide evidence regarding its metabolic competence and its potential economic value.

Bioremediation of heavy metals polluted environment and decolourization of black liquor using microbial biofilms

BACKGROUND

With increased urbanization and industrialization, modern life has led to an anthropogenic impact on the biosphere. Heavy metals pollution and pollutants from black liquor (BL) have caused severe effects on environment and living organisms. Bacterial biofilm has potential to remediate heavy metals and remove BL from the environment. Hence, this study was planned to investigate the potential of microbial biofilms for the bioremediation of heavy metals and BL polluted environments.

METHODS AND RESULTS

Eleven biofilm forming bacterial strains (SB1, SB2, SC1, AF1, 5A, BC-1, BC-2, BC-3, BC-4, BC-5 and BC-6) were isolated and identified upto species level via 16S rRNA gene sequencing. Biofilm strains belonging to Bacillus and Lysinibacillus sphaericus were used to remediate heavy metals (Pb, Ni, Mn, Zn, Cu, and Co). Atomic absorption spectroscopy showed significantly high (P ≤ 0.05) bioremediation potential by L. sphaericus biofilm (1462.0 ± 0.67 µgmL^-1) against zinc (Zn). Similarly, Pseudomonas putida biofilm significantly (P ≤ 0.05) decolourized (65.1%) BL. Fourier transform infrared (FTIR) analysis of treated heavy metals showed the shifting of major peaks (1637 & 1629-1647, 1633 & 1635-1643, and 1638-1633 cm^-1) corresponding to specific amide groups due to C = O stretching.

CONCLUSION

The study suggested that biofilm of the microbial flora from tanneries and pulp paper effluents possesses a strong potential for heavy metals bioremediation and BL decolourization. To our knowledge, this is the first report showing promising biofilm remediation potential of bacterial flora of tanneries and pulp-paper effluent from Kasur and Sheikhupura, Punjab, Pakistan, against heavy metals and BL.

Comparative analysis of the catalysis and stability of the native, recombinant and metagenomic alkaline proteases in organic solvents

The effect of organic solvents on alkaline proteases was assessed for native, recombinant, and metagenomically derived alkaline proteases. Their stability and the effects of physicochemical parameters were studied in the presence of hexane. The native enzyme was comparatively more resistant against the organic solvents than the recombinant counterparts. On the other hand, the metagenomically derived alkaline protease was minimally resistant against solvents. A similar trend was apparent for the stability of enzyme in organic solvents. The novelty of this study lies in the fact that the majority of the studies on the solvent tolerance have focused on the mesophilic enzymes, while those from the haloalkaliphilic bacteria have received little attention. The comparative tolerance of the native, recombinant, and metagenomic alkaline proteases against the organic solvent has practical importance. The phylogenetic relatedness among the various protease sequences will be described.