Asian Journal of Microbiology and Biotechnology

Biodegradation of Nitroaromatic Compounds by Alkaliphilic Bacteria: Mechanisms, Applications and Future Perspectives

Rani J. Rathod — 2026-06-06

Nitroaromatic compounds are extensively utilized in various industries; however, their toxic and persistent nature creates serious environmental and health concerns. Conventional treatment methods are frequently costly and may not provide complete pollutant removal. The paper summarizes the classification and characteristics of alkaliphilic bacteria, describes the enzymatic mechanisms involved in nitroaromatic reduction, and highlights recent research findings from laboratory and field studies. Key applications in environmental bioremediation are highlighted. Current challenges, such as slow degradation rates and limited genetic understanding, are also discussed. The review concludes that alkaliphilic bacteria offer a promising, eco-friendly solution for treating nitroaromatic-contaminated sites adapted to alkaline environments in which many ordinary microorganisms fail to survive. Although microbial biodegradation has been widely investigated, comparatively limited attention has been given to alkaliphilic bacteria and their degradation potential under alkaline conditions. Furthermore, information regarding their enzymatic mechanisms, degradation efficiency, and environmental applications remains scattered across the available literature.

Endophytic Microbes: Natural Entities for Sustainable Agriculture and Human Health

Ankit Tiwari — 2026-06-09

Sustainable agriculture and human health can be significantly impacted by endophytic microbes. These microbes are the important component of the plant holobiont. By facilitating nutrient acquisition, producing phytohormones, and secreting stress relieving enzymes, these endophytic microbes support the plant growth and increase crop resistance against both biotic and abiotic stresses. Their ability to form symbiotic relationships without harming the host allows them to function as natural bio-stimulants and biocontrol agents, promoting environmental sustainability. Additionally, endophytes are known for the efficient production of different types of bioactive secondary metabolites, such as terpenoids, peptides, alkaloids, and polyketides, which possess strong antimicrobial, antioxidant, anticancer, and immunomodulatory properties. These compounds offer promising opportunities for new drug discovery to combat the increasing global challenge of drug resistance, which can provide aid and relief in all aspects of human life. Recent advancements in multi-omics techniques have enhanced our knowledge about the diversity of endophytic microorganisms, colonization strategies, and their functional capabilities across various plant species and environments. Therefore, the exploration of endophytic microbes can effectively address the dual challenges of enhancing agricultural productivity to meet increasing food demands and managing the pharmaceutical with naturally derived therapeutics. In this review, we discuss current insights regarding endophytic microbial diversity, colonization strategies, their roles in promoting plant growth, and their applications in the fields of sustainable agriculture and human health.

Microbial Biomass, Organic Carbon and Basal Soil Respiration: Indicators for Initialization of Microbial Community in Manganese Mine Spoil of Koira, Sundergarh, Odisha, India

Samapika Dash — 2026-05-29

The quantification of microbial biomass is instrumental in evaluating soil degradation and restoration, as it significantly influences nutrient cycling and organic matter turnover, as well as soil structural and functional stability in response to perturbations and management practices. This study aimed to assess the potential effects of microbial biomass, organic carbon, moisture content and basal soil respiration on the establishment of microbial colonies in relation to the fertility of various age series of mine spoil. The chronosequence manganese overburden mine spoils taken in the study are: fresh manganese overburden mine spoil, i.e., 0 yr (MBO0), 2 yr manganese overburden mine spoil (MBO2), 4yrs manganese overburden mine spoil (MBO4), 6 yrs manganese overburden mine spoil (MBO6), 8 yrs manganese overburden mine spoil (MBO8), 10 yrs manganese overburden mine spoil (MBO10). The analysis revealed an increase in microbial biomass carbon, nitrogen and phosphorus (MB-C, MB-N, MB-P), from MBO0 to MBO10. The percentage of organic carbon and moisture content exhibited an increasing trend across overburden spoil, supporting the progressive establishment of microbes. Microbial respiration increased from MBO0 to MBO10; this rise was probably caused by the organic carbon content gradually increasing. From MBO0 to MBO10, the number of colony-forming units of Azotobacter (AZB), Arthrobacter (ARB), Rhizobium (RHZ), Heterotrophic Aerobes (HAB), Yeast (YST), Actinomycetes (ACT), and Fungus (FUN) increased. The largest population was found in forest soil that helped initiate succession in mine-disturbed areas, while sulfur-reducing bacteria (SRB) showed the opposite trend. Multivariate analysis of variance (MANOVA) shown, HAB pertains highest (99.3%) contribution towards variations among all microbial colonies.

Characterization by MALDI TOF Mass Spectrometry of Yeast and Lactic Acid Bacteria Isolated from ogi and Their Antibacterial Activity

Adesokan Isaac Ayanniran — 2026-06-05

Ogi is a Nigerian traditional fermented food commonly produced from maize, millet and/or sorghum. It serves as cheap breakfast meal for low income earners and complimentary meal for infants and convenient for the sick, convalescent and the elderly. It is produced by submerged fermentation and lactic acid bacteria and yeasts have been isolated as responsible for its fermentation. Consumption of ogi has many advantages which include enhanced nutritional value, digestibility, therapeutic benefits and safety against pathogens. Determining the protein profiles of microorganisms using MALDI-TOF (Matrix-assisted laser desorption-ionization time of flight) mass spectrometry are compatible with the results of identification obtained by molecular methods. MALDI-TOF MS are robust, reliable as well as fast and inexpensive to identify Gram-positive bacteria such as LAB and yeast isolates. In this study LAB and yeast isolates were identified using MALDI TOF MS and their antibacterial activity was determined using the agar disc diffusion assay. The 91 LAB isolates identified by the above named method belong to 12 different species. The LAB strain with the highest percentage of occurrence of 59% is Lactiplantibacillus plantarum and it is followed by Limosilactobacillus fermentum which had a percentage of occurrence of 15%. The lowest percentage of occurrence obtained was 1.1% which was recorded for Companilactobacillus pabuli, Enterococcus faecalis, Lactococuss allomyrinae and so on. A total of 43 yeasts were identified and they belong to 5 different species and these are Issatchenkia orientalis (34.9%), Geotrichum candidum (27.9), Pichia occidentalis (32.6), Candida rugosa (1%) and C. tropicalis (1%). The result of antibacterial activity shows that only 26 LAB isolates inhibited at least one of the spoilage and pathogenic organisms employed as indicator. The highest diameter of zone of inhibition (10.8 mm) recorded for L. plantarum OG58 against Escherichia coli while none of the LAB isolates was able to inhibit Bacillus subtilis. The method employed for identification of LAB and yeast isolates from ogi revealed the presence of certain strains which have not been reported before. Also, the LAB strains were able to inhibit the indicator organism tested to varying degree with exception of B. subtilis.

Isolation, Identification and Antimicrobial Sensitivity Pattern of Bacteria Causing Egg Peritonitis in Layer Birds

Shanmugasundaram Udhayavel — 2026-06-15

Egg peritonitis is an important reproductive disorder of commercial layer chickens and is commonly associated with bacterial infection of the peritoneal cavity. The present study was conducted to isolate and identify bacterial agents associated with egg peritonitis in commercial layer birds and to determine their in vitro antimicrobial sensitivity pattern. Peritoneal swabs were collected from 50 commercial layer birds showing gross lesions suggestive of egg peritonitis during necropsy examination at the Poultry Disease Diagnosis and Surveillance Laboratory, Namakkal, Tamil Nadu, India, from May 2019 to March 2020. The affected birds belonged to different age groups ranging from 21 to 72 weeks and included Lohman, Bovans, Babcock and Hyline strains. Samples were processed using standard bacteriological methods. Isolates were identified based on cultural characteristics, staining reaction, morphology and biochemical tests. Antimicrobial susceptibility testing was performed by the disc diffusion method using selected antibacterial agents. Among the 50 samples examined, Escherichia coli was the most frequently isolated bacterium, accounting for 35 isolates (70%). Other bacteria isolated were Salmonella species in 4 samples (8%), Proteus species in 4 samples (8%), Klebsiella species in 3 samples (6%), Pseudomonas species in 3 samples (6%) and Gallibacterium species in 1 sample (2%). The highest overall sensitivity was observed to levofloxacin, with 32 isolates (64%) showing sensitivity, followed by ciprofloxacin with 30 isolates (60%). Sensitivity to co-trimoxazole, gentamicin, ampicillin, chlortetracycline and amoxicillin was 32%, 22%, 18%, 4% and 2%, respectively. No sensitivity was observed to neomycin, tylosin, lincomycin, bacitracin, colistin and erythromycin. The findings indicate that E. coli was the predominant bacterial agent associated with egg peritonitis in the examined layer birds, and fluoroquinolones showed comparatively higher in vitro activity against the isolates.

Evaluation of Antifungal Activities of Silver Nanoparticles Impregnated Hydrogel for Advanced Biomedical Applications

Sakshi Chaudhary — 2026-06-15

Fungal contamination of wounds and biomedical surfaces remains a relevant challenge in infection management, and hydrogel-based antimicrobial materials may provide a useful platform for localized protection. In this study, a silver nanoparticle-loaded hydrogel was prepared using a κ-carrageenan, polyethylene glycol, and polyvinylpyrrolidone polymer matrix and evaluated for antifungal activity against Aspergillus niger. The hydrogel formulation was prepared by blending aqueous polymer solutions, followed by incorporation of silver nanoparticles at 10 ppm and potassium chloride-mediated stabilization. The resulting AgNP-loaded hydrogel formed a uniform sheet with a light brown appearance, while the nanoparticle-free hydrogel served as the control. Antifungal activity was assessed using two in vitro models representing contaminated and freshly exposed wound-like conditions. In the treatment model, A. niger was spread over agar plates, and hydrogel sheets were placed on the inoculated surface. The AgNP-loaded hydrogel produced visible inhibition of fungal growth at the hydrogel–agar interface, whereas the control hydrogel did not show comparable antifungal activity. In the preventive model, a biphasic nutrient-containing hydrogel system was prepared with one half containing AgNPs and the other half without nanoparticles. After inoculation with A. niger, fungal growth was observed on the control side, while the AgNP-containing region showed visible suppression of colonization. These findings indicate that incorporation of AgNPs into the κ-carrageenan/PEG/PVP hydrogel matrix retained antifungal activity under the tested in vitro conditions. Further physicochemical characterization, quantitative antifungal analysis, cytocompatibility testing, and in vivo evaluation are required before biomedical application can be established.