Search Results (36)

Soil salinization and selenium (Se) deficiency threaten global food security. This study developed a composite bioinoculant combining ACC deaminase-producing Serratia liquefaciens and biogenically synthesized nano-selenium (SeNPs) to alleviate saline–alkali stress and enhance Se nutrition in rice (Oryza sativa L.). A strain of S. liquefaciens with high ACC deaminase activity was isolated and used to biosynthesize SeNPs with stable physicochemical properties. Pot experiments showed that application of the composite inoculant (S3: S. liquefaciens + 40 mmol/L SeNPs) significantly improved seedling biomass (fresh weight +53.8%, dry weight +60.6%), plant height (+31.6%), and root activity under saline–alkali conditions. S3 treatment also enhanced panicle weight, seed-setting rate, and grain Se content (234.13 μg/kg), meeting national Se-enriched rice standards. Moreover, it increased rhizosphere soil N, P, and K availability and improved microbial α-diversity. This is the first comprehensive demonstration that a synergistic bioformulation of ACC deaminase PGPR and biogenic SeNPs effectively mitigates saline–alkali stress, enhances soil fertility, and enables safe Se biofortification in rice. Full article

Several strains of the genus Serratia isolated from the rhizosphere of crops are plant growth-promoting bacteria (PGPB) that may possess various traits associated with nitrogen metabolism, auxin production, and other characteristics. The objective of the present study was to investigate the in vitro and in vivo characteristics of the growth-promoting activity of S. liquefaciens UNJFSC 002 in potato plants. This strain was inoculated into potato varieties (Solanum tuberosum) under laboratory and greenhouse conditions to determine the bacterial strain’s ability to promote growth under controlled conditions. It was found that the S. liquefaciens strain UNJFSC 002 had a significantly greater effect on the fresh and dry weight of the foliage and induced a higher tuber weight per plant and larger tuber diameter compared to the uninoculated potato plants (p < 0.05). Additionally, in vitro, the strain demonstrated the ability to fix atmospheric nitrogen and produce indole-3-acetic acid (IAA), as well as the capacity to solubilise tricalcium phosphate in the laboratory. This research reveals the potential of S. liquefaciens UNJFSC 002 as an inoculant to improve potato production, demonstrating its ability to promote the growth and productivity of potato varieties suitable for direct consumption and processing under controlled conditions. Full article

Sodium nitrite is an additive commonly used in meat processing to provide technological effects. However, the presence of nitrates in food can lead to the formation of carcinogenic N-nitrosamines; so, its use should be limited. This study concerns the possibility of reducing sodium nitrite (III) addition in the production of canned meat to 50 mg/kg by enriching the product with tomato peels and seeds powder (TPSP). The aim of this study was to evaluate the effect of TPSP on the physicochemical, chemical and microbiological quality of canned pork. Four different products were tested in this study: a control sample and samples with the addition of 0.5%, 1.5%, and 2.5% tomato peels and seeds powder. The addition of TPSP decreased the pH values of meat products and increased yellowness (b*) and redness (a*) values. The influence of TPSP on the increase in antioxidant activity of canned meat was also observed. However, the plant-based additive did not affect the chemical composition or water activity of the tested product. The control samples were characterized by a lower TBARS compared to the other samples of meat products. Microbiological analysis results indicate that the canned pork samples meet the product requirements. The most commonly isolated species from the samples were Enterobacter cloacae, Serratia liquefaciens, and Enterococcus faecalis. Full article

The quality modification of chilled, raw conditioned mutton (RCM) after storage significantly impacts consumer preferences, making shelf-life extension and quality preservation crucial. This study evaluated the effects of sodium diacetate (SDA), sodium dehydroacetate (DHA-S), ε-polylysine hydrochloride (PLH), and nisin on RCM quality and bacterial community at concentrations of 3.0, 0.50, 0.30, and 0.50 g/kg, respectively. Major spoilage bacteria were isolated, and the inhibitory effects of these preservatives were studied, leading to the development of compound preservatives. TVC increased significantly during RCM preparation, with continuous increases in TVC and TVB-N levels throughout storage, reaching spoilage thresholds by day 5. Bacterial diversity decreased markedly, with Brochothrix and Pseudomonas dominating. SDA effectively inhibited TVC proliferation and TVB-N formation, maintaining bacterial diversity and reducing Brochothrix and Pseudomonas abundance while promoting the growth of lactic acid bacteria. Five spoilage bacteria strains were isolated, including Serratia liquefaciens B2107-1, a potent meat spoilage bacterium under refrigeration. PLH and SDA demonstrated significant inhibitory activity against this bacterium, with minimum inhibitory concentrations (MICs) of 0.175 and 0.400 mg/mL, respectively. Combining PLH and SDA at 1MIC + 3MIC exhibited a synergistic antimicrobial effect, maintaining RCM quality with reduced SDA usage. These findings demonstrate the significant potential of these preservatives in chilled, raw meat products. Full article

In the present work, the impact of three new bacterial strains and their consortium on composting was evaluated using textile waste as a main substrate mixed with paper, cardboard and green waste, The effectiveness of these micro-organisms in accelerating organic matter degradation was tested. For bioaugmentation of composting, three concentrations (4%, 6% and 8%) were applied. Among the three strains tested, one strain and the consortium demonstrated high organic matter degradation potential, achieving a total organic carbon concentration between 19–21%, total Kjeldahl nitrogen between 1.29–1.56%, a C/N ratio between 13–16%, and a temperature exceeding 55 °C. In the current study, mature compost was attained in 10 weeks, instead of the 44 weeks required for conventional composting and the 12 weeks achieved with other strains previously used. Identification of the strains by 16S rRNA sequencing revealed that they belonged to Bacillus sp., Paenibacillus sp., and Enterobacter aerogenes, respectively. These strains are recognized for their remarkable potential to breakdown a broad variety of organic matter, including lignocellulosic molecules. Furthermore, incorporation of bacteria into the waste mixture (either separately or as a consortium) extended the thermophilic phase by 2 weeks in this study, especially Bacillus sp., Paenibacillus sp. and consortium, leading to a significant reduction in compost production time. It is noteworthy that the efficacy of these strains was considerably greater compared with the three previous strains (i.e., Streptomyces cellulosae, Achromobacter xylosoxidans and Serratia liquefaciens), which were isolated from compost and used for bioaugmentation in a previous study. Our results demonstrate that bioaugmentation by endogenous microbial strains and/or their consortium significantly accelerates the composting process. Full article

Plant-growth-promoting rhizobacteria (PGPR), in addition to their well-known direct effects on plant growth and development, have been reported to be effective in plant abiotic (trace metal, drought, etc.) and biotic (phytopathogens, insects, etc.) stress management. PGPRs are involved in shaping the fate of trace metals in the rhizosphere and plants and thus may also reduce trace metal stress in plants. The aims of our study were to isolate and select indigenous trace-metal-resistant PGP strains and investigate their effects on maize germination and early development. The roles of the two selected strains, Pseudomonas koreensis and Serratia liquefaciens isolated from trace-metal-contaminated soil were investigated to mitigate trace metal stress in 21-day-old Zea mays seedlings. In the present study, 13 bacterial strains were isolated and screened for PGP traits under normal and trace metal stress conditions. The effect of two selected strains was further studied on plant experiments. The germination process, plant growth parameters (length, weight, dry matter content), photosynthetic activity, GPOX activity, trace metal accumulation, and translocation in microbes inoculated Cd (0.5 mM), Zn (1 mM), and Cd + Zn (0.1 + 0.5 mM) treated maize plants was studied. Our results revealed that trace metal toxicity, in terms germination and growth parameters and antioxidant enzyme activity, was enhanced upon inoculation with Pseudomonas koreensis BB2.A.1. Chlorophyll content and accumulation studies showed enhanced results following inoculation with Serratia liquefaciens BB2.1.1. Therefore, both bacterial strains possessed beneficial traits that enabled them to reduce metal toxicity in maize. Full article

In recent years, the use of natural preservatives in food products has gained significant attention due to their potential health benefits and effectiveness. A standardized microbiological analysis was conducted on Slovak farm-produced lump goat cheese samples to determine the antibacterial activity of dry herbs and essential oils added to vacuum-packed goat cheese. We employed five dried herbs and five essential oils derived from the same plants. The microbiological quality of 145 fresh and vacuum-packed goat cheese samples was assessed. The number of coliform bacteria, total viable count, lactic acid bacteria, and microscopic filamentous fungi were examined in raw cheese samples stored for 12 days at 4 °C. All cheese samples were vacuum-packed (control samples were packed without vacuum). This study evaluated the potential benefits of using essential oils and dried herbs from thyme (Thymus serpyllum L.), black pepper (Piper nigrum L.), clove (Eugenia caryophyllus Thunb.), mint (Mentha × piperita L.), and basil (Ocimum basilicum L.) as preservatives. The essential oils were obtained from Hanus Ltd., Nitra, Slovakia, and were applied at a concentration of 2%. The dried herbs were obtained from Popradský čaj (Poprad, Slovakia) and Mäspoma Ltd. (Zvolen, Slovakia). The results showed that all microorganism groups were significantly reduced in cheese samples following the application of essential oils throughout the entire storage period. During the preservation of cheese samples in polyethylene bags used for vacuum packing food, Lactococcus garvieae, L. lactis, Enterobacter cloacae, and Serratia liquefaciens were the most frequently isolated microbiota. Essential oils and dried herbs demonstrated antimicrobial potential during the storage of vacuum-packed goat cheese. Full article

Due to the high microbiological contamination of raw food materials and the increase in the incidence of multidrug-resistant bacteria, new methods of ensuring microbiological food safety are being sought. One solution may be to use bacteriophages (so-called phages) as natural bacterial enemies. Therefore, the aim of this study was the biological and genomic characterization of three newly isolated Serratia- and Enterobacter-specific virulent bacteriophages as potential candidates for food biocontrol. Serratia phage KKP_3708 (vB_Sli-IAFB_3708), Serratia phage KKP_3709 (vB_Sma-IAFB_3709), and Enterobacter phage KKP_3711 (vB_Ecl-IAFB_3711) were isolated from municipal sewage against Serratia liquefaciens strain KKP 3654, Serratia marcescens strain KKP 3687, and Enterobacter cloacae strain KKP 3684, respectively. The effect of phage addition at different multiplicity of infection (MOI) rates on the growth kinetics of the bacterial hosts was determined using a Bioscreen C Pro growth analyzer. The phages retained high activity in a wide temperature range (from −20 °C to 60 °C) and active acidity values (pH from 3 to 12). Based on transmission electron microscopy (TEM) imaging and whole-genome sequencing (WGS), the isolated bacteriophages belong to the tailed bacteriophages from the Caudoviricetes class. Genomic analysis revealed that the phages have linear double-stranded DNA of size 40,461 bp (Serratia phage KKP_3708), 67,890 bp (Serratia phage KKP_3709), and 113,711 bp (Enterobacter phage KKP_3711). No virulence, toxins, or antibiotic resistance genes were detected in the phage genomes. The lack of lysogenic markers indicates that all three bacteriophages may be potential candidates for food biocontrol. Full article

Biogas has long been used as a household cooking fuel in many tropical counties, and it has the potential to be a significant energy source beyond household cooking fuel. In this study, we describe the use of low electrical energy input in an anaerobic digestion process using a microbial electrochemical cell (MEC) to promote methane content in biogas at 18, 28, and 37 °C. Although the maximum amount of biogas production was at 37 °C (25 cm³), biogas could be effectively produced at lower temperatures, i.e., 18 (13 cm³) and 28 °C (19 cm³), with an external 2 V power input. The biogas production of 13 cm³ obtained at 18 °C was ~65-fold higher than the biogas produced without an external power supply (0.2 cm³). This was further enhanced by 23% using carbon-nanotubes-treated (CNT) graphite electrodes. This suggests that the MEC can be operated at as low as 18 °C and still produce significant amounts of biogas. The share of CH₄ in biogas produced in the controls was 30%, whereas the biogas produced in an MEC had 80% CH₄. The MEC effectively reduced COD to 42%, whereas it consumed 98% of reducing sugars. Accordingly, it is a suitable method for waste/manure treatment. Molecular characterization using 16s rRNA sequencing confirmed the presence of methanogenic bacteria, viz., Serratia liquefaciens and Zoballella taiwanensis, in the inoculum used for the fermentation. Consistent with recent studies, we believe that electromethanogenesis will play a significant role in the production of value-added products and improve the management of waste by converting it to energy. Full article

Microbial community succession in raw milk determines its quality and storage period. In this study, carbon dioxide (CO₂) at 2000 ppm was used to treat raw milk to investigate the mechanism of extending the shelf life of raw milk by CO₂ treatment from the viewpoint of microbial colonies and metabolites. The results showed that the shelf life of CO₂-treated raw milk was extended to 16 days at 4 °C, while that of the control raw milk was only 6 days. Microbiomics analysis identified 221 amplicon sequence variants (ASVs) in raw milk, and the alpha diversity of microbial communities increased (p < 0.05) with the extension of storage time. Among them, Pseudomonas, Actinobacteria and Serratia were the major microbial genera responsible for the deterioration of raw milk, with a percentage of 85.7%. A combined metagenomics and metabolomics analysis revealed that microorganisms altered the levels of metabolites, such as pyruvic acid, glutamic acid, 5′-cmp, arginine, 2-propenoic acid and phenylalanine, in the raw milk through metabolic activities, such as ABC transporters, pyrimidine metabolism, arginine and proline metabolism and phenylalanine metabolism, and reduced the shelf life of raw milk. CO₂ treatment prolonged the shelf life of raw milk by inhibiting the growth of Gram-negative aerobic bacteria, such as Acinetobacter guillouiae, Pseudomonas fluorescens, Serratia liquefaciens and Pseudomonas simiae. Full article

The role of bats in the global microbial ecology no doubt is significant due to their unique immune responses, ability to fly, and long lifespan, all contributing to pathogen spread. Some of these animals hibernate during winter, which results in the altering of their physiology. However, gut microbiota shifts during hibernation is little studied. In this research, we studied cultivable gut microbiota composition and diversity of Nyctalus noctula before, during, and after hibernation in a bat rehabilitation center. Gut microorganisms were isolated on a broad spectrum of culture media, counted, and identified with mass spectrometry. Linear modeling was used to investigate associations between microorganism abundance and N. noctula physiological status, and alpha- and beta-diversity indexes were used to explore diversity changes. As a result, most notable changes were observed in Serratia liquefaciens, Hafnia alvei, Staphylococcus sciuri, and Staphylococcus xylosus, which were significantly more highly abundant in hibernating bats, while Citrobacter freundii, Klebsiella oxytoca, Providencia rettgeri, Citrobacter braakii, and Pedicoccus pentosaceus were more abundant in active bats before hibernation. The alpha-diversity was the lowest in hibernating bats, while the beta-diversity differed significantly among all studied periods. Overall, this study shows that hibernation contributes to changes in bat cultivable gut microbiota composition and diversity. Full article

Small mammals are bioindicator organisms, and, through their gut microbiota (GM), could be carriers of pathogens and resistant bacteria. Also, wild GM composition has been suggested to have large implications for conservation efforts. Seventeen bacterial species were obtained from intestinal samples of Bulgarian yellow-necked mice (Apodemus flavicollis) and bank voles (Myodes glareolus) via classic microbiological cultivation and biochemical identification. Twelve Gram-negative—Escherichia coli, Yersinia enterocolitica, Yersinia kristensenii, Hafnia alvei, Serratia liquefaciens, Serratia marcescens, Serratia proteamaculans, Pseudescherichia vulneris, Klebsiella pneumoniae ssp. ozaenae, Enterobacter cloacea, Pantoea agglomerans, Pseudomonas fluorescens group—and five Gram-positive bacteria, Enterococcus faecium, Enterococcus faecalis, Enterococcus hirae, Bacillus thuringiensis, and Lysinibacillus sphaericus, were discovered. Enterobacteriaceae was the most abundant family. The isolates belonged to one of the major reported taxa in rodents, Firmicutes (the Gram-positive species) and to the less abundant, but still among the first, phyla, Proteobacteria (the Gram-negative strains). We did not find any members of the other major phylum, Bacteroidetes, likely due to lack of metagenomic techniques. E. coli and Y. enterocolitica were confirmed with polymerase chain reaction. Almost all strains had pathogenic potential, but the good condition of the test animals suggests their commensal role. The Y. enterocolitica strains did not have the ail pathogenicity gene. There was high prevalence of multi-drug resistance (MDR), but for the expected species with high level of intrinsic resistance, such as the enterococci and S. marcescens. E. coli and some other species had very low antimicrobial resistance (AMR), in line with other studies of wild rodents. Many of the strains had biotechnological potential; e.g., B. thuringiensis is the most used biological insecticide, with its proteins incorporated into the Bt genetically modified maize. The GM of the tested wild mice and voles from Bulgaria proved to be a source of bacterial diversity; many of the strains were promising in terms of biotechnology, and, in addition, the samples did not contain the African swine fever virus. Full article

Microorganisms are key to balancing marine ecosystems and have complex interactions at the ocean–atmosphere interface, affecting global climate and human health. This research investigated the diversity of cultivable bacteria and fungi in marine bioaerosols in the North Tropical Atlantic Ocean. Using the technique of spontaneous sedimentation in selective culture media, samples were collected during oceanographic expeditions. After isolation and purification, microbial strains were identified by phenotypic and genetic analyses. Fungi isolated included Acrophialophora, Aspergillus, Chrysosporium, Cladosporium, Fonsecaea, Mucor, Rhodotorula, Schizophyllum, Stemphylium, Candida, Curvularia, Cystobasidium, Exophiala, Neotestudina, Penicillium, Pestalotiopsis, and Preussia. The bacterial isolates belonged to the Bacillota, Pseudomonadota, Enterobacteriaceae family, Bacillus genus, and Serratia liquefaciens groups. About 40% of bacteria and 42% of fungi were identified as potential human pathogens, suggesting a relationship between human actions and the microbiota present in bioaerosols on the high seas. Sea surface temperature (SST) and wind speed influenced microorganisms. More studies and analyses in different scenarios should be conducted considering environmental and climate variables in order to deepen knowledge and generate information on the subject, so that standards can be established, and quality parameters determined. Full article

White rot, caused by Stromatinia cepivora (Anamorph: Sclerotium cepivorum Berk), is a serious soil-borne disease of the onion that restricts its cultivation and production worldwide. Herein, we isolated and characterized a plant growth-promoting rhizobacterium Stenotrophomonas maltophilia from healthy onion roots and an endophytic bacterium Serratia liquefaciens from healthy bean leaves. Both isolates showed strong fungistatic activity against S. cepivora using the dual culture and culture filtrate methods. This effect might be due to the presence of several volatile compounds, especially menthol in both culture filtrates as shown with a GC-MS analysis. Additionally, the root drench application of cell-free culture filtrates of S. maltophilia and S. liquefaciens significantly reduced the incidence and severity of white rot disease on treated onion plants, which was associated with the activation of both enzymatic (POX and PPO) and non-enzymatic (phenolics and flavonoids) antioxidant defense machineries of S. cepivora-infected onion plants. Moreover, the culture filtrates of both bacterial bioagents remarkably enhanced the growth (as expressed by root length, plant height, and number of leaves) and yield parameters (as indicated by bulb circumference, fresh weight of the bulb, and bulb yield per plot) of treated onion plants under field conditions during two successive seasons (2020/2021 and 2021/2022). This might be because of a reduced disease severity and/or the accumulation of the main auxin, indole-3-acetic acid (IAA), and its precursor, the amino acid tryptophan. Our findings suggest that both bioagents might be utilized as eco-friendly alternative control measures to reduce the utilization of chemical fungicides entirely or partially for the safer production of onion in S. cepivora-infested soils. Full article

Microbial interactions play an important role in initial cell adhesion and the endurance of biofilm toward disinfectant stresses. The present study aimed to evaluate the effect of microbial interactions on biofilm formation and the disinfecting activity of an innovative photocatalytic surfactant based on TiO₂ nanoparticles. Listeria monocytogenes, Salmonella Enteritidis, Escherichia coli, Leuconostoc spp., Latilactobacillus sakei, Serratia liquefaciens, Serratia proteomaculans, Citrobacter freundii, Hafnia alvei, Proteus vulgaris, Pseudomonas fragi, and Brochothrix thermosphacta left to form mono- or dual-species biofilms on stainless steel (SS) coupons. The effectiveness of the photocatalytic disinfectant after 2 h of exposure under UV light on biofilm decontamination was evaluated. The effect of one parameter i.e., exposure to UV or disinfectant, was also determined. According to the obtained results, the microbial load of a mature biofilm depended on the different species or dual species that had adhered to the surface, while the presence of other species could affect the biofilm population of a specific microbe (p < 0.05). The disinfectant strengthened the antimicrobial activity of UV, as, in most cases, the remaining biofilm population was below the detection limit of the method. Moreover, the presence of more than one species affected the resistance of the biofilm cells to UV and the disinfectant (p < 0.05). In conclusion, this study confirms that microbial interactions affected biofilm formation and decontamination, and it demonstrates the effectiveness of the surfactant with the photocatalytic TiO₂ agent, suggesting that it could be an alternative agent with which to disinfect contaminated surfaces. Full article