Microbiology Research Journal International

Examining the Function of Metabolites Generated from Cyanobacteria as Antimicrobial Agents from a 21st-Century Perspective

2026-07-09T12:51:18+00:00

Cyanobacteria are among the oldest oxygenic photosynthetic organisms on Earth and occupy an extraordinarily broad range of ecological niches, from marine and freshwater systems to extreme terrestrial habitats. Their capacity to withstand intense ultraviolet radiation, desiccation, nutrient scarcity and microbial competition is underpinned by a rich biosynthetic repertoire of secondary metabolites, many of which display potent antibacterial, antifungal and antiviral activities. This review examines the chemical diversity, biosynthetic origin and mechanisms of action of cyanobacterial antimicrobial metabolites, situating the discussion within the contemporary crisis of antimicrobial resistance and the stagnation of conventional antibiotic discovery pipelines. Cyclic and linear peptides, alkaloids, polyketides, macrolides, lipids and lectins isolated predominantly from filamentous genera such as Nostoc, Lyngbya, Moorea, Fischerella, Calothrix and Anabaena are discussed with reference to their molecular targets, which include bacterial RNA polymerase, fungal ergosterol-rich membranes, viral envelope glycoproteins and components of the bacterial cell wall and electron transport chain. The contribution of non-ribosomal peptide synthetase and polyketide synthase gene clusters to this chemical diversity is examined alongside genome-mining approaches that have accelerated the discovery of cryptic biosynthetic pathways. Biotechnological obstacles to translating laboratory findings into clinically usable agents, including low and inconsistent yields, cultivation scale-up difficulties, structural complexity and the toxicological profile of certain cyanobacterial metabolites, are critically appraised, together with emerging nanoformulation strategies intended to overcome bioavailability constraints. The review concludes that cyanobacteria represent a comparatively underexploited reservoir of structurally novel antimicrobial chemotypes that merit sustained, mechanistically grounded investigation, while acknowledging that translational progress remains constrained by supply, safety and regulatory hurdles that have yet to be systematically resolved.

Antimicrobial Profiling of Selected Medicinal Plants from West Pokot, Kenya: Plant Parts and Concentration-Specific Effects

2026-07-02T05:49:28+00:00

Antimicrobial resistance has increased interest in evaluating medicinal plants as potential sources of bioactive compounds. This study evaluated the antibacterial and antifungal activities of selected medicinal plants from West Pokot County, Kenya, and determined the effects of plant part and extract concentration on antimicrobial activity. Leaf, stem bark, and root extracts of Lannea fulva, Ochna insculpta, Pittosporum viridiflorum, Schrebera alata, and Teclea pilosa were evaluated against four bacterial pathogens (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus cereus) and two fungal pathogens (Aspergillus fumigatus and Candida albicans). Antimicrobial activity was assessed using agar diffusion methods, with ciprofloxacin and amphotericin B as positive controls and dimethyl sulfoxide as the negative control. Data were analyzed using factorial analysis of variance, and mean separation was performed at p ≤ 0.05. The results showed that antimicrobial activity varied significantly with plant species, plant part, extract concentration, and microbial strain. Root extracts demonstrated higher antibacterial activity (mean inhibition zone = 10.773 mm) compared with leaf (9.936 mm) and stem bark extracts (9.241 mm). Among the crude extracts, Pittosporum viridiflorum root extract recorded the highest antibacterial activity in the plant-part comparison, producing an inhibition zone of 16.694 mm against E. coli. In concentration-based assays, P. viridiflorum root extract showed the highest antibacterial response against E. coli (22.11 mm) at 100% concentration. Antifungal activity differed significantly among plant species, plant parts, and concentrations. The highest antifungal activity among plant extracts was recorded in Schrebera alata root extract against A. fumigatus, producing an inhibition zone of 14.422 mm at 125% concentration. Amphotericin B produced the highest overall inhibition against fungal pathogens (15.081–16.057 mm), whereas dimethyl sulfoxide showed no meaningful activity (3.000 mm). The findings demonstrate that selected medicinal plants from West Pokot possess measurable antibacterial and antifungal properties, with clear plant part and concentration-dependent variations. Further phytochemical characterization, minimum inhibitory concentration determination, and toxicity evaluation are recommended before therapeutic application.

Effect of Biofertilization with a Mixture of Arbuscular Mycorrhizal Fungi and Natural Phosphate from Tilemsi on the Growth and Grain Yield of Sorghum (Sorghum bicolor L. Moench) in the Field in Koumantou

2026-07-03T13:50:26+00:00

Sorghum is an important food-security crop in Mali, but productivity is often constrained by poor soil fertility, particularly low phosphorus availability. Arbuscular mycorrhizal fungi and locally available natural phosphate may provide an alternative or complementary approach to mineral fertilisation. This study evaluated the effect of biofertilisation with a mixture of arbuscular mycorrhizal fungi and Tilemsi natural phosphate on sorghum growth and grain yield under field conditions in Koumantou, Bougouni region, Mali. The experiment used a randomised block design with five treatments and four replications: an uninoculated and unfertilised control, mineral fertiliser, Tilemsi natural phosphate, arbuscular mycorrhizal fungal inoculum, and the inoculum combined with Tilemsi natural phosphate. The fungal inoculum comprised Rhizophagus irregulare, Glomus aggregatum, and Glomus mosseae. Plant height and stem diameter were measured during growth, while panicle length, panicle weight, dry aboveground biomass, grain yield, and 1000-grain weight were assessed at harvest. The experimental soil was acidic and low in organic matter, nitrogen, potassium, and available phosphorus. Fertilised and inoculated treatments generally improved growth compared with the control. At 100 days after emergence, plant height ranged from 195.06 cm in the control to 216.28 cm under mineral fertiliser; the combined treatment reached 214.03 cm. Dry aboveground biomass was highest under the combined treatment (39.31 g) compared with the control (22.44 g). Grain yield was also numerically higher under the combined treatment than under the control. These findings suggest that arbuscular mycorrhizal fungi combined with Tilemsi natural phosphate may support sorghum growth in phosphorus-poor field conditions.

Antibacterial, Bactericidal and Membrane-Disruptive Activities of Essential Oils from Callistemon salignus, Croton gratissimus and Melaleuca bracteata against Reference Enterococcus Species

2026-07-09T12:55:43+00:00

The increasing occurrence of antimicrobial-resistant Enterococcus species has encouraged the investigation of plant-derived products with antibacterial potential. This study evaluated the antibacterial, bactericidal, and membrane-disruptive activities of essential oils obtained from the leaves of Callistemon salignus, Croton gratissimus, and Melaleuca bracteata against five reference Enterococcus species: Enterococcus avium, Enterococcus casseliflavus, Enterococcus hirae, Enterococcus gallinarum, and Enterococcus faecalis. Antibacterial activity was assessed by agar disc diffusion, while minimum inhibitory concentration and minimum bactericidal concentration values were determined using broth microdilution-based methods. Bactericidal potential was further interpreted using MBC/MIC ratios, and membrane-disruptive activity was evaluated using membrane-damage indices. All tested essential oils produced measurable inhibition against at least some of the Enterococcus species, with inhibition zones ranging from 9.0 to 12.0 mm, compared with 25 to 47 mm for ciprofloxacin. Melaleuca bracteata essential oil showed the strongest overall activity, with MIC values ranging from 2.5 to 5.0 mg/mL and MBC values of 5.0 to >5.0 mg/mL. Callistemon salignus showed moderate activity, with MIC values from 2.5 to >5.0 mg/mL and MBC values of 5.0 to >5.0 mg/mL. Croton gratissimus showed comparatively weaker activity, with MIC values of 5.0 to >5.0 mg/mL and no detectable bactericidal activity within the tested concentration range. Membrane-damage indices were highest for M. bracteata against E. avium and E. faecalis. Overall, the findings indicate that M. bracteata and C. salignus possess measurable antibacterial effects against reference Enterococcus species, with membrane disruption likely contributing to their activity.

Seroprevalence and Combined Profiles of IgM/IgG Antibodies against SARS-CoV-2 in Ambulatory Patients in Yaoundé, Cameroon

2026-07-15T10:34:45+00:00

Aims: The study aims to assess the seroprevalence of anti-SARS-CoV-2 IgM and IgG antibodies among ambulatory patients in Yaoundé and to identify clinical and demographic correlates associated with the humoral immune response.

Methods: An analytical cross-sectional study was conducted from February to July 2024 at the Central Hospital of Yaoundé. A probability sample of 350 adult patients was recruited. IgM and IgG antibodies were detected using indirect ELISA. Statistical analysis included the chi-square test, with a significance threshold of p < 0.05, multivariate logistic regression and multiple correspondence analysis (MCA).

Results: The study population was predominantly female (55.7%). The adjusted overall seroprevalence was 26.67% for IgM and 53.73% for IgG. Analysis of combined immune responses revealed that 39.49% of patients were IgM+/IgG−, 50.21% were IgM−/IgG+ and 60.50% were IgM+/IgG+. Asthenia (39.7%) and myalgia (35.1%) were the most frequent clinical manifestations. Multivariate logistic regression identified IgM status as the only statistically significant determinant of IgG presence (p = 0.012). MCA confirmed the limited discriminative power of symptoms with respect to serological status.

Conclusion: The study indicates a high level of exposure to SARS-CoV-2. The predominance of the IgM+/IgG+ profile suggests either an active infection phase or an important immunological transition within the hospital population, underscoring the need for continuous surveillance.

Occurrence and Antimicrobial Resistance Profiles of Pseudomonas aeruginosa Isolated from Urine and Soil Samples in Selected Healthcare Facilities in Lafia, Nigeria

2026-07-18T13:19:42+00:00

Background: Pseudomonas aeruginosa is an opportunistic Gram-negative bacterium associated with healthcare-related infections and environmental persistence. Its ability to develop antimicrobial resistance is an important public health concern in clinical and environmental settings.

Aim: This study assessed the occurrence, antimicrobial susceptibility profile, and multidrug-resistance pattern of P. aeruginosa isolated from urine and soil samples obtained from selected healthcare facilities in Lafia Metropolis, Nasarawa State, Nigeria. Exploratory plasmid profiling and curing were undertaken in selected multidrug-resistant isolates.

Methods: A total of 135 samples, comprising 90 midstream urine samples and 45 soil samples, were collected from three healthcare facilities between February and May 2023. Isolation and identification of P. aeruginosa were performed using standard microbiological and biochemical procedures. Antimicrobial susceptibility testing was carried out using the Kirby–Bauer disc diffusion method. Multidrug-resistance patterns and multiple-antibiotic-resistance index values were determined. Selected multidrug-resistant isolates underwent plasmid profiling and acridine-orange treatment, followed by repeat susceptibility testing.

Results: Pseudomonas aeruginosa was recovered from 62.2% of soil samples and 26.7% of urine samples; there were no statistically significant differences between healthcare facilities. Resistance was highest to ampicillin, nalidixic acid, and amoxicillin–clavulanate, whereas ciprofloxacin showed no resistance among the tested isolates. Multiple-antibiotic-resistance index values ranged from 0.3 to 0.8. In six selected multidrug-resistant isolates, plasmid bands were observed and resistance phenotypes changed after acridine-orange treatment in several isolates.

Conclusion: Antimicrobial-resistant P. aeruginosa occurred in both urine and soil samples from the study area. The plasmid profiling and curing findings provide preliminary evidence of a possible plasmid contribution to resistance phenotypes, but they do not identify plasmid-borne resistance genes or confirm plasmid-mediated resistance. Routine surveillance, antimicrobial stewardship, environmental hygiene and confirmatory molecular studies are recommended.

Synergistic Effect of Microbially Enriched Farm Yard Manure on Growth, Biomass and Nutrient Dynamics of Chickpea (Cicer arietinum L.)

2026-07-20T12:58:08+00:00

Microbial enrichment of organic manure is a highly sustainable strategy for enhancing leguminous crop productivity. A pot-culture experiment was conducted to evaluate the efficacy of farmyard manure (FYM) enriched with individual and multi-strain microbial inoculants—phosphate-solubilising bacteria (PSB), Azotobacter, Rhizobium, and Bacillus circulans—for improving the morphological growth, biomass accumulation, and nutrient assimilation of chickpea (var. RVG-202). Before sowing, a 30-day incubation period showed that the consortium treatment (T₆) recorded the highest viable microbial population (10.2 × 10⁵ CFU/g) in FYM. The crop was harvested at 65 days after sowing (DAS). The consortium treatment was superior to the individual-strain treatments and the uninoculated control. Application of the multi-strain consortium resulted in significantly greater plant height at 65 DAS (35.93 cm) and shoot dry weight (4.91 g/plant). Moreover, the Rhizobium and consortium treatments significantly enhanced root biomass compared with the other treatments. Straw nitrogen content did not differ significantly among treatments, possibly because of a nutrient-dilution effect; however, the consortium treatment resulted in significantly greater total uptake of nitrogen (60.39 mg/plant), phosphorus (17.18 mg/plant), and potassium (42.71 mg/plant). The findings indicate that enriching FYM with a suitable multi-strain microbial consortium creates a favourable microbial environment that enhances root biomass, vegetative growth, and nutrient acquisition in chickpea, indicating its potential for bio-organic crop nutrition under controlled pot-culture conditions.