Biology subjects

Muleta, D.

Publications and source records attributed to Muleta, D..

6 recordsLinked to original sources

bioRxiv2025

Genome analysis of Lactobacillus plantarum and Lactobacillus brevis isolated from traditionally fermented Ethiopian kocho and their probiotic properties

Probiotics are essential for promoting health, with lactic acid bacteria (LAB) from traditional fermented foods like Ethiopian kocho offering valuable benefits. The objective of this study was to systematically analyse the genomic characteristics, bacteriocin production, and probiotic potential of LAB strains isolated from fermented Ethiopian kocho. The research involved isolating LAB from kocho, assessing their tolerance to acid and bile salts, evaluating antimicrobial activity, determining antibiotic susceptibility, and conducting whole-genome sequencing (WGS) to investigate genetic relatedness. Out of 150 LAB isolates, 7 (4.67%) exhibited remarkable acid tolerance, surviving at rates between 50.52-74.05% and 33.33-62.40% after 3 and 6 hours of exposure to pH 2, respectively. These seven acid-tolerant isolates also demonstrated exceptional resistance to 0.3% bile salt, maintaining survival rates ranging from 88.96% to 98.10% over 24 hours. In addition, the isolates displayed inhibitory effects against several important foodborne pathogenic bacteria, underscoring their potential as natural antimicrobial agents. Antibiotic susceptibility testing revealed that all isolates were susceptible to ampicillin, tetracycline, and erythromycin, whereas the most potent isolates exhibited significant resistance to kanamycin. Notably, four of the seven isolates showed resistance to streptomycin, while the remaining three were sensitive. The WGS analysis revealed that the isolates belonged to the Lactobacillus genus, including six Lactobacillus plantarum strains and one Lactobacillus brevis strain. Genomic analysis using the Bayesian Analysis of Gene Essentiality (BAGEL) tool predicted the presence of two class II bacteriocins across all seven strains, further supporting their potential as functional probiotic candidates. Overall, our findings highlight the probiotic potential of the seven Lactobacillus strains, demonstrating their acid and bile salt tolerance, antimicrobial properties, and genetic predisposition for bacteriocin production.

microbiology↗

bioRxiv2024

Enhancing pigment production by a chromogenic bacterium (Exiguobacterium aurantiacum) using tomato waste extract: A Statistical approach

There is high demand for microbial pigments as promising alternative for synthetic pigments basically for safety and economic reasons. This study aimed at the optimization of yellowish-orange pigment production by Exiguobacterium aurantiacum using agro-waste extract as growth substrate. Air samples were collected using depositional method. Pure cultures of pigment producing bacteria were isolated by subsequent culturing on fresh nutrient agar medium and the potent isolate was identified using MALDI-TOF technique. Culture conditions were screened using Plackett-Burman design and the most three significant variables were optimized by response surface methodology. Fermentation was conducted in 150 mL agro-waste decoctions from which tomato waste extract was selected because of higher optical density of the culture compared to other agro-waste extracts. Pigment was extracted by solvent extraction method and the best solvent was selected based on its ability to dissolve the culture suspension. The pigment was characterized using spectroscopic and chromatographic techniques. Culture agitation rate, initial medium pH and concentration of yeast extract were identified as the most significant (p< 0.0001) variables affecting pigment production. At optimized conditions, 0.96 g/L of pigment was extracted from 4.73 g/L of culture biomass and the extracted pigment under optimized conditions was 1.6 times higher than the pigment extracted under un-optimized conditions. The spectroscopic and chromatographic analyses demonstrated the presence of different functional groups and carotenoids were identified as parts of the molecule responsible for the yellowish-orange pigmentation of the extract. This study demonstrated the potential for optimization of pigment production by bacteria using agro-waste extract as substrate. Hence, the current findings strongly encourage for further study at a large-scale level for industrial production.

microbiology↗

bioRxiv2024

Genetic Diversity of Zymoseptoria tritici Populations in Central and South-eastern Ethiopia

Septoria tritici blotch (STB), caused by the hemibiotrophic fungus Zymoseptoria tritici, is a serious threat to global wheat production, and a major bottleneck to wheat production in Ethiopia. Accurate identification and analysis of the pathogens genetic structure helps inform robust STB management. This study analyzed the molecular identity and genetic structure of 200 Z. tritici isolates retrieved from diseased crops in central and south-eastern regions of Ethiopia. Allelic diversity at 12 simple sequence repeat (SSR) loci was examined for all 200 isolates, and 165 isolates were identified by Sanger sequencing of the internal transcribed spacer (ITS) region of nuclear DNA (rDNA) region. The microsatellites were highly polymorphic, with mean number of alleles (Na) = 6.23, effective alleles (Ne) =2.90, Neis gene diversity (H) =0.57, and polymorphic information content (PIC) =0.59, and an analysis of molecular variance confirmed the presence of low population differentiation (Fixation Index (FST) = 0.02, Gene Flow (Nm) = 14.7), with 95% of the total genetic variation residing within populations, and only 5% residing between populations. The highest genetic diversity (Number of allele (Na) = 9.33, Effective number of allele (Ne) = 3.41 and Neis gene diversity (H) = 0.68) was observed in the Oromia special zone surrounding Finfinnee (OSZ) Z. tritici populations, followed by Arsi and North Shewa populations, indicating that these areas are ideal for multi-location germplasm resistance screening, and also pathogen genetic and genomic analyses. Cluster analyses did not clearly divide the populations into genetically separate clusters according to their geographic sampling areas, probably because of high gene flow. All individual samples showed genetic admixture, and shared genomic backgrounds from two subgroups (K=2). Overall, the SSR markers proved to be highly informative and effective genetic tools for unlocking the pathogens genetic structure. The Z. tritici populations of central and southeast Ethiopia exhibit high genetic diversity, indicating the need to deploy durable and diverse disease management strategies. North Shewa, OSZ, Arsi and West Arsi administrative zones represent hotspots for genetic and genomic analyses of Z. tritici. Moreover, these areas would be excellent locations for host-pathogen interaction studies, and wheat germplasm screening for STB resistance.

plant biology↗

bioRxiv2024

Plant Development Drives Dynamic Shifts in the Root Compartment Microbiomes of Wild and Domesticated Finger Millet Cultivars

BackgroundPlant-microbe interactions in two root compartments - the rhizosphere and endosphere - play vital roles in maintaining plant health and ecosystem dynamics. The microbial communities in these niches are shaped in complex ways by factors including the plants developmental stage and cultivar, and the compartment where the interactions occur. Different plant cultivars provide distinct nutritional and ecological niches and may selectively enrich specific microbial populations through the secretion of root exudates. This gives rise to complex and dynamic plant-microbe interactions; some cultivars promote the recruitment of beneficial symbionts while others may deter pathogens. To clarify these processes, this work investigated the structure of the endosphere and rhizosphere microbial communities of wild type finger millet and five domesticated cultivars across two plant developmental stages. ResultsOur results showed that the plant developmental stage, compartment, and cultivar have varying degrees of impact on root-associated microbiomes. The dominant bacterial phyla in all samples were Proteobacteria, Actinobacteria, and Bacteroidetes, while the dominant fungal phyla were Ascomycota and Basidiomycota. All of these phyla exhibited pronounced variations in abundance. In general, an increased abundance of Actinobacteria in the endosphere was accompanied by a reduced abundance of Proteobacteria. The most pronounced changes in microbial community structure were observed in the rhizosphere during the flowering stage. Changes in the microbiome patterns of the rhizosphere were driven predominantly by the genus Pseudomonas. Moreover, the host plants developmental stage strongly influenced the microbial communities, suggesting that plants can recruit specific taxa based on their need for particular soil consortia. ConclusionsOur results show that both host developmental stage and domestication strongly affect the assembly and structure of the plant microbiome. Moreover, plant root compartments can selectively recruit specific taxa from associated core microbial communities to fulfill their needs in a manner that depends on both the plants developmental stage and the specific root compartment that is involved. These findings show that deterministic selection pressures exerted by plants during their growth and development can significantly affect their microbial communities and have important implications for efforts to create tools for manipulating the microbiome to sustainably improve primary productivity.

microbiology↗

bioRxiv2019

In vitro evaluation of probiotic properties of lactic acid bacteria isolated from some traditionally fermented Ethiopian food products

Probiotics are live microorganisms which when consumed in large number together with a food promote the health of the consumer. The aim of this study was to evaluate in vitro probiotic properties of lactic acid bacteria (LAB) isolated from traditional Ethiopian fermented Teff injera dough, Ergo and Kocho products. A total of 90 LAB were isolated, of which 4 (4.44%) isolates showed 45.35-97.11% and 38.40-90.49% survival rate at pH values (2, 2.5 and 3) for 3 and 6 h in that order. The four acid tolerant isolates were found tolerant to 0.3% bile salt for 24 h with 91.37 to 97.22% rate of survival. The acid-and-bile salt tolerant LAB isolates were found inhibiting some foodborne test pathogenic bacteria to varying degrees. All acid-and-bile tolerant isolates displayed varying sensitivity to different antibiotics. The in vitro adherence to stainless steel plates of the 4 screened probiotic LAB isolates were ranged from 32.75 to 36.30% adhesion rate. The four efficient probiotic LAB isolates that belonged to Lactobacillus species were identified to strain level using 16S rDNA gene sequence comparisons and namely were Lactobacillus plantarum strain CIP 103151, Lactobacillus paracasei subsp. tolerans strain NBRC 15906, Lactobacillus paracasei strain NBRC 15889 and Lactobacillus plantarum strain JCM 1149. The four Lactobacillus strains were found to have potentially useful to produce probiotic products.

microbiology↗

bioRxiv2019

Optimization of the cultivation conditions of indigenous wild yeasts and evaluation of their leavening capacity: Isolated from fermented foods and beverages.

Ethiopia has a high demand for bakers yeast in the bread and beverage industries. Unfortunately, Ethiopia has no producing plant for bakers yeast and instead relies on costly imports. The objective of this work was to identify the most productive and useful indigenous bakers yeasts isolated from local fermented foods and drinks, honey and Molasses using leavening ability as the major metric. Six of the test isolates produced a maximum cell mass at 30{degrees}C, pH of 5.5 and 48 hours of incubation. Isolate AAUTf1 did not produce hydrogen sulfide, while isolates AAUTf5, AAUTj15 and AAUSh17 produced low levels of this chemical, and isolates AAUMl20 and AAUWt21 produced high levels of hydrogen sulfide, neglecting their utility in baking. The leavening performance of isolates AAUTf1 (Candida humilis) and AAUTf5 (Kazachstania bulderi) had the highest dough volume of 131 cm3 and 128 cm3 respectively in 120 min. Isolates AAUSh17 (Saccharomyces cerevisiae) and AAUTj15 (Saccharomyces cerevisiae) raised the dough volume of 127 cm3 and 125 cm3 respectively, at 60 min compared to commercial yeast (117 cm3 in 90 min). The study also revealed that mixed cultures of indigenous yeasts had better leavening capacity than single cultures. The co-inoculated cultures of AAUTf1 + AAUTf5 + AAUTj15, AAUTf5 + AAUTj15, and AAUTf1 + AAUTj15 + AAUSh17 reached 143 cm3 at 90 min, 141 cm3 and 140 cm3 both at 60 min, respectively. Thus, the indigenous isolates are candidates for optimizing utilization of yeast for fast promotion and utilization in the bakery industries.

microbiology↗