International Microbiology最新文献

This study is aimed at evaluating the efficacy of essential oil-based microemulsions in combination with antimicrobials against Mycoplasma gallisepticum (MG), a major respiratory pathogen in poultry. MG was isolated from 1.1% of broiler and 0.5% of breeder flocks, with the highest incidence recorded during winter and autumn, particularly in farms located in Giza and Sharkia governorates. Among 37 confirmed isolates, eight were positive for the mgc2 gene, while six carried gapA and crmA. Cumin, camphor, and olive microemulsions exhibited favorable physicochemical characteristics. GC-MS analysis identified α-citral, ( +)-2-bornanone, and cis-vaccenic acid as the major components of cumin, camphor, and olive oils, respectively. Notably, olive/camphor and cumin microemulsions were rich in cis-vaccenic acid and linoleoyl chloride, respectively. Antibiotic susceptibility testing revealed that all isolates were resistant to lincomycin, erythromycin, spectinomycin, and tiamulin, with 50% exhibiting complete resistance to all antibiotics. Tylosin showed partial activity, inhibiting 37.5% of isolates (MIC 0.25-4 µg/mL). Camphor microemulsion demonstrated the highest antimicrobial effect (MIC 0.08-5 µg/mL). The most significant synergistic interaction was observed between cumin oil and either oxytetracycline or spiramycin, as well as between camphor microemulsion and doxycycline against MG isolates. Furthermore, combination treatments significantly downregulated the expression of mgc2, crmA, and gapA genes. These findings highlight the promising role of essential oil-based microemulsions as effective adjuncts in MG control strategies.

Environmental pollution by heavy metals is a major global concern, necessitating the exploration of sustainable bioremediation strategies. Airborne bacteria represent an underexplored resource in this context. This study investigated the potential of bacteria isolated from bioaerosols for the bioremediation of heavy metals. Nine bacterial strains belonging to the genera Exiguobacterium, Kocuria, Rhodococcus, and Staphylococcus were isolated and identified through MaLDI-TOF analysis and 16S rRNA gene sequencing. The minimum inhibitory concentrations (MIC) of chromium, copper, lead, nickel, mercury, and cadmium were determined to evaluate metal resistance. Bioreduction assays were performed to determine the capacity of selected strains to reduce hexavalent chromium [Cr(VI)] in solution. Chromate reductase activity was quantified in Rhodococcus rhodochrous As33. Morphological responses to chromium exposure were examined using scanning and transmission electron microscopy (SEM and TEM). MIC analyses revealed variable but significant resistance to multiple Heavy metals among the isolates. Bioreduction assays demonstrated that five selected strains reduced from 79.9% to 100% of Cr(VI) within 72 h. R. rhodochrous As33 achieved complete Cr(VI) reduction, as confirmed by 1,5-diphenylcarbazide complexation, and inductively coupled plasma mass spectrometry (ICP-MS). Enzymatic analysis indicated a chromate reductase activity of 67.87 U mg⁻¹ of total protein in this strain. SEM and TEM revealed marked cellular adaptations to chromium stress, including pleomorphism, membrane thinning, vesicle formation, and the deposition of extracellular electron-dense precipitates, suggesting active biosorption and bioprecipitation mechanisms. The results highlight the bioremediation potential of airborne bacteria, particularly R. rhodochrous As33, in heavy metal-contaminated environments. Further studies are needed to validate their performance under complex environmental conditions and to support their application in sustainable remediation strategies.

Pseudomonas aeruginosa (P. aeruginosa) represents a critical global health challenge due to its escalating antibiotic resistance and its formidable ability to form protective biofilms, necessitating the urgent development of novel therapeutic strategies. This research explores the potential of allicin, a natural antibacterial compound, encapsulated within alginate-casein (ACAN) nanoparticles as a promising approach to combat multidrug-resistant (MDR) P. aeruginosa proliferation and biofilm formation. The ACAN nanoparticles were comprehensively characterized for their morphological traits using FESEM, DLS, and FTIR, confirming successful allicin encapsulation and enhanced stability. Notably, the ACAN formulation demonstrated significantly improved antibacterial efficacy and a profound ability to inhibit biofilm growth. Specifically, ACAN nanoparticles achieved up to 77% inhibition of P. aeruginosa biofilm growth, a statistically significant improvement compared to free allicin (e.g., ~ 28% inhibition). Furthermore, the study investigated the impact of ACAN on key biofilm-related genes, revealing a marked downregulation of pslG (involved in exopolysaccharide production) and lasI (critical for quorum sensing and biofilm maturation). These findings collectively highlight that encapsulating allicin within alginate-casein nanoparticles not only enhances its stability and delivery but also significantly boosts its efficacy against the persistent biofilm-forming capabilities of MDR P. aeruginosa. This novel ACAN platform thus presents a compelling and promising therapeutic strategy for addressing challenging bacterial infections.

The objective of this research was to assess whether halquinol, a zootechnical antimicrobial, can lead to cross-resistance to antibiotics of importance in human and animal health. The minimum inhibitory and bactericidal concentrations of halquinol against 37 Salmonella and Escherichia coli strains/isolates were determined, along with their resistance profiles against 14 antibiotics used in human and veterinary medicine. Sublethal exposure to halquinol was performed to evaluate the acquisition of resistance to the compound by determining new minimum inhibitory and bactericidal concentrations. Cross-resistance to other antibiotics was examined by establishing a new resistance profile after sublethal exposure and comparing it with the previous results. Resistance to halquinol was successfully induced; prior to sublethal exposure, concentrations ranging from 18.25 to 300 µg/mL were required for bacterial inhibition, whereas following sublethal exposure, these values increased to 75 to 1200 µg/mL. The induction of halquinol resistance also impacted resistance to human and veterinary antibiotics. For example, before sublethal exposure to halquinol, 71.4% of Salmonella isolates were resistant to cephalexin; after sublethal exposure, 100% of the isolates exhibited resistance. In E. coli, the percentage of azithromycin-resistant isolates increased from 66.7 to 100% following sublethal exposure. These findings indicate that halquinol, in addition to inducing resistance to itself, may also promote resistance to essential drugs in both human and veterinary medicine. Further studies, particularly molecular investigations, are necessary for a comprehensive characterization of the observed in vitro effects and to determine whether these findings are replicated in vivo.

Microbacterium esteraromaticum, a common bacterium utilized in the degradation of organic pollutants, is prevalently found in the wastewater environments of rural areas. However, the excessive use of antibiotics in recent years has endowed M. esteraromaticum with a broad spectrum of antibiotic resistance, transforming it into a potential high-risk contaminant capable of disseminating antibiotic resistance genes (ARGs) within the environment. Lytic bacteriophages, due to their characteristic ability to lysogenize and specifically target host bacteria, have emerged as potent biocontrol agents. In this study, a specific bacteriophage, CASP3, targeting the multi-drug resistant M. esteraromaticum (MDR-ME), was isolated from a wastewater treatment facility. The assessment of phage CASP3 revealed several noteworthy characteristics, including good tolerance and a targeted effect against multidrug-resistant MDR-ME. Studies observed that CASP3, to some extent, reduced the ARGs carried by its host. Furthermore, it demonstrated good environmental compatibility, with no significant potential risks identified. The successful isolation of CASP3 not only provides a new addition to phage resources targeting this bacterium but also offers a potential biocontrol tool for mitigating ARG dissemination and reducing public health risks in rural areas.

Rapidly developing sustainability raises concerns about the role of nanoparticles in environmental applications; however, the influence of these nanoparticles on fungal cellulase activity remains unclear. The present research assessed the role of nanoparticles as magnetic iron oxide (Fe₃O₄) and zinc oxide (ZnO) on cellulase activity using two selected fungal species. Two fungal species, Trichoderma parareesei and Aspergillus costaricensis, were studied. A pure fungal culture was cultivated for its cellulase production using rice husk as substrate to check the role of nanoparticles in its hydrolytic efficiency. After 4 days of incubation at a pH of 5 and a temperature of 30 °C, the two pure cultures of fungal species proved to be efficient in cellulase activity on rice husk. The cellulase production of T. parareesei using rice husk as substrate was the highest compared to the control and to A. costaricensis. It appeared that nanoparticles significantly enhanced cellulase activity of the two studied fungal species, which are effective in rice husk degradation. The optimal concentration of Fe₃O₄ nanoparticles was found to be 20 ppm for T. parareesei and 300 ppm for A. costaricensis, while the optimal concentration of ZnO nanoparticles was 2.5 ppm and 7.5 ppm for T. parareesei and A. costaricensis, respectively. At these concentrations, maximum cellulase activity using Fe₃O₄ NPs reached 0.244 FPU/mL for T. parareesei and 0.106 FPU/mL for A. costaricensis, revealing 12-fold and fivefold enhancement compared to the untreated control. Additionally, the treatment with ZnO NPs resulted in higher cellulase productivity, reaching 0.203 FPU/mL and 0.111 FPU/mL for T. parareesei and A. costaricensis, respectively.

Selenium, an essential micronutrient that cannot be endogenously synthesized by mammals, requires exogenous dietary supplementation. Lactic acid bacteria can biotransform sodium selenite (Na₂SeO₃) into bioavailable selenium nanoparticles (SeNPs), creating multifunctional selenium-enriched forages. This study systematically assessed the synergy of SeNPs and Pediococcus acidilactici in alfalfa silage through four treatments: control (CK), P. acidilactici alone (LP), Na₂SeO₃ alone (Se), and combined treatment (LPSe). After 30 days of ensiling, fermentation quality, microbial community, and aerobic stability were determined. The results revealed that LPSe silage exhibited decreased pH, butyric acid, and binding protein contents compared with CK, while its organic selenium content (1.64 mg/kg DM) was Significantly higher than that of LP Silage. 16S rRNA sequencing showed increased abundance of Pediococcus and Lactobacillus in LPSe Silage with Simplified bacterial community structure. After 7 days of aerobic exposure, CK Silage showed rapid pH and ammonia Nitrogen increase, whereas LPSe Silage had 28.24% longer aerobic stability than CK and 11.50% longer than LP. These results demonstrate LPSe as the optimal treatment for alfalfa silage.

Oleaginous fungi, as a vital part of the microbiota in naturally diverse ecosystems, represent a reservoir for biomass-based lipid production. The challenge is the selection of promising strains with cost-effective operation for multiple applications. In the current study, 12 fungal strains were isolated and screened for their oleaginicity. All strains were fermented and accumulated over 20% lipids in their cell dry weight (CDW). After the preliminary screening, one strain was genetically identified as Gongronella butleri HMA-10 due to its maximum biomass (15.8 ± 0.8 g/L) and lipid (40.6 ± 1.7%) yields. Moreover, the HMA-10 was subjected to optimization of various parameters with the help of response surface methodology (RSM) for maximum lipid accumulation. The selected strain was fermented on fructose associated with a combination of sodium nitrite and yeast extract, exhibiting optimum nutritional conditions with a C/N ratio of (40:1). Cultivation conditions (4 days, 27.5 ℃, and pH of 7.0) resulted in the highest CDW and lipid content. Scaling up of HMA-10 in bioreactor fermentation under optimized conditions significantly induced biomass and lipid content (19.5 g/L and 53%), compared with shake flask fermentation (15.8 ± 0.8 g/L and 40.6 ± 1.7%), respectively. Fatty acid (FA) profile was confirmed by gas chromatography (GC) analysis, and the results revealed that oleic acid (OA) was the predominant (46.91%), while palmitic acid (PA), linoleic acid (LA), and γ-linolenic acid (GLA) were found in significant quantities (21.13, 9.67, and 8.06%), respectively. This study employed for the first time G. butleri HMA-10 as a promising candidate for high lipid accumulation with a potential second-generation biodiesel production in large-scale industrialization.

In this study, the biocontrol and plant growth-promoting properties of Pseudomonas chlororaphis VUPF5 were comprehensively evaluated using a series of in vitro biochemical assays. The strain showed strong enzymatic activities, such as the production of cellulase and protease, which contribute to nutrient recycling and degradation of pathogenic fungal structures. In addition, the ability to solubilize phosphate, produce siderophores, HCN, and indole-3-acetic acid (IAA) underscores its versatile potential to promote plant health and control pathogens through both direct and indirect mechanisms. To improve the viability and efficiency of the VUPF5 strain under environmental stress, it was encapsulated with a composite matrix of sodium alginate and soy protein isolate (SPI). Structural characterization by XRD, FTIR, and SEM confirmed the formation of a stable, biocompatible microcapsule with high encapsulation efficiency (approx. 84%) and controlled release over 55 days. These capsules protected the bacteria from environmental fluctuations while allowing their gradual release, ensuring sustained bioactivity in the soil. Greenhouse trials with pistachio seedlings infected with Phytophthora drechsleri showed that plants treated with microcapsules had an 87% disease control rate, outperforming both the free bacterial suspension and control groups. Interestingly, even empty capsules showed moderate protection, likely due to the bioactive nature of SPI, suggesting an additive effect in strengthening plant defenses. Overall, VUPF5 is a promising dual-function bioinoculant that improves plant growth and disease control. Encapsulation enhances its survival, release, and contribution to plant resistance, thus supporting sustainable agriculture.

The long-term sustainability of food production and the usage of agricultural land are seriously threatened by soil salinization. To combat the salinization, the salt-tolerant cyanobacteria can be a potent candidate. However, it is not yet clear how these microbes work to remediate saline soil. Salinity is a global problem, mainly caused by higher evaporation rate, low rainfall, seawater intrusion into freshwater, overuse of chemical fertilizers, etc. This study examined the effect of various salt concentrations on Desertifilum salkalinema SSAU 7 (SSAU 7), which is isolated from the river Ganges, Prayagraj, India. This study examined the tolerance of microbes by analysing the chlorophyll-a, carotenoid, carbohydrate, and photosynthetic activity. It also includes the activity of trehalose and antioxidants, for the mechanism involved in the tolerance and providing new insights that will help the development of cyanobacteria bio-stimulants capable of ameliorating the adverse effects of salinity. The findings revealed that the strain SSAU 7 has the ability to survive up to 20 gL^-1 salt concentrations efficiently. The study showed that the halotolerant cyanobacterium can not only survive at high salt concentration but also it can help in Cicer arietinum (chickpea) plant growth by secreting Indole acetic acid. With increased germination percentage of seed, stem, and root length, SSAU 7 clearly had a good impact on plant growth. These results highlight how cyanobacteria enormously combat salt stress efficiently and can also promote the production of crops while reducing the negative impact of agrochemicals on the environment.