This study investigated the prevalence of Listeria spp. in Bangladesh and determined their hemolytic activity. A total of 103 samples, including cattle farm water, feed, raw milk, cow dung, and soil, were collected from 24 farms. Isolation was performed using Listeria enrichment broth and selective agar, followed by polymerase chain reaction (PCR) confirmation targeting the prs gene. Hemolytic activity of the isolates was determined using 5% sheep blood agar. Results reveal that the geographic location had a significant impact on the prevalence, with Sylhet division displaying the highest prevalence and Rangpur showing no presence of these pathogens. However, the sample type did not have any association with prevalence. A statistically significant correlation was found between the presence of Listeria spp. with elevated levels of fecal coliforms, suggesting common environmental or contamination sources. Investigation of the virulence potential of the Listeria isolates based on their hemolytic pattern on blood agar demonstrated that 1 of 2 of the Listeria spp. from soil samples were â-hemolytic, while no â-hemolysis was observed among isolates from cattle farm water, and cattle feed samples. The highest diversity of hemolysis patterns was observed for isolates from raw milk (Shannon index = 1.10, Simpson index = 3.00) and cow dung (Shannon index = 0.94, Simpson index = 2.36). Isolates from cattle feed samples showed the lowest diversity (Shannon index = 0.50, Simpson index = 1.47). In case of divisions, Dhaka showed the highest diversity (Shannon index = 0.97, Simpson index = 2.40) while the lowest diversity was observed in Barisal (Shannon index = 0.50, Simpson index = 1.47). In conclusion, the findings indicate a significant geographical variation in Listeria prevalence and highlight the role of environmental contamination in its occurrence. These results underscore the need for improved hygiene and monitoring strategies to mitigate public health risks. Bangla. J. Microbiol. 2025, Vol. 41, P: 1-11
Dormant cysts of brine shrimp (Artemia) are exclusively imported as a feed source for aquaculture industries in Bangladesh. Despite their high nutritional value, the potential introduction of exotic bacterial flora upon hatching is a growing concern. This study characterizes the bacterial community associated with commonly used Artemia cysts in Bangladesh and assesses their pathogenic potential following the current hatchery protocol. Using culture-based methods, 33 bacterial strains were isolated from encapsulated cysts post-hatching under gnotobiotic conditions. Through subsequent biochemical and 16S rRNA gene-based sequencing, 21 bacterial strains from different origins were identified as belonging to the genera Pseudomonas (n=9), Klebsiella (n=3), Enterobacter (n=4), Ralstonia (n=1), Aeromonas (n=1), and Vibrio (n=3). All 21 isolates exhibited á-hemolytic (n=8) and â-hemolytic (n=13) activities on blood agar, indicating their pathogenicity. Six of the isolated bacteria (one each from the identified genus) exhibited significant casein-protease activity and caused significant mortality in Artemia nauplii, with LD50 values ranging from 6.1 x 108 CFU/mL to 9.7 x 108 CFU/mL. The presence of these pathogenic bacteria in Artemia cysts suggests a potential biohazard, warranting their evaluation before introduction into hatcheries in Bangladesh. Bangla. J. Microbiol. 2025, Vol. 41, P: 1-8
Tuberculosis, mainly caused by Mycobacterium tuberculosis, is a serious bacterial infection that primarily infects the respiratory system but can spread to other organs of the body. Approximately one-third of the world’s population is infected with MTB, affecting people from all age groups. Out of the 30 high TB burden countries, 6 of them are in South-East Asia (SEA) region accounting for 44% of the global TB burden. This review looks at the distribution of TB cases within the SEA region. It further explores some of the underlying causes of drug-resistant TB throughout history and how human activities has led to its proliferation. Different phenotypic and molecular methods in diagnosing drugresistant TB are also discussed in this review. Comparative analysis between the different methods have also been made in this review. In order to eradicate TB, emphasis must be put on efficient diagnostic techniques, preventative measures and adequate treatment. Bangla. J. Microbiol. 2025, Vol. 41, P: 1-8
The accumulation of immune effector cells often exacerbates inflammatory response. This study assessed the therapeutic effects of Lactiplantibacillus plantarum PQ104969 on gastrointestinal inflammation induced by subacute administration of indomethacin in Wistar albino rats with emphasis of the effect on the stomach, ileum and colon. Twenty-four (24) male Wistar rats were divided into four groups: control group A received normal saline; group B were induced with indomethacin (7 mg/kg); group C were treated with 5 x 107 CFU/ml L. plantarum PQ104969, while positive control group D were treated with Omeprazole (20 mg/kg). The stomach, ileum and colon of all groups were harvested after 7 days treatment and analyzed for their organ weight, malondialdehyde (MDA) concentration, glutathione (GSH) level, total antioxidant capacity (TAC) and protein concentration. Serum level of interleukin 10 (IL10) and immunoglobulin g (IgG) were determined using ELISA technique. Tissue histology of the selected organs was done using routine haematoxylin and eosin staining technique. L. plantarum PQ104969-treated group had significantly higher glutathione levels and reduced MDA levels in the colon compared to the indomethacin group. The total antioxidant capacity (TAC) was elevated in this group, though lower than in the positive control. Both L. plantarum and omeprazole groups experienced a reduction in relative colon weight, while protein concentrations in gastrointestinal organs were consistent across groups. An increase in IL10 and IgG levels, along with milder epithelial erosion, indicated reduced inflammation. The study demonstrates that L. plantarum PQ104969 mitigates indomethacin-induced gastrointestinal damage in Wistar rats through antioxidant and immunomodulatory mechanisms, which offer a promising therapeutic approach for gastrointestinal damages. Bangla. J. Microbiol. 2025, Vol. 41, P: 1-10
Bacillus thuringiensis (Bt) is a bacterium widely known for its pesticidal properties, with numerous serovars exhibiting diverse ecological adaptations and pathogenic characteristics. In this study, we performed a comprehensive genomic analysis of 82 Bacillus thuringiensis serovars retrieved from GenBank, with the aim of investigating their core and pan-genome structures, genomic variation, and genetic relationships. Core and pan-genome analyses revealed a highly conserved core genome consisting of 3279 clusters, indicative of essential functional genes common to all studied serovars. In contrast, the pan-genome was vast, encompassing 25,447 clusters, underscoring the genetic diversity and adaptability of the species. Upset analysis of gene content revealed a range of overlap in genomic sequences among serovars, with shared core genes and strain-specific genes potentially explaining functional diversity. Average Nucleotide Identity (ANI) analysis showed substantial genetic divergence among serovars, with some exhibiting over 99% similarity, while others, such as Bacillus thuringiensis navarrensis, were more genetically distant. These findings enhance our understanding of the genomic architecture of Bacillus thuringiensis, providing insights into its genomic evolution. Bangla. J. Microbiol. 2025, Vol. 41, P: 1-10
The paradise threadfin, Polynemus paradiseus, is an anadromous fish in Bangladesh that enters the freshwater river system from saline water (the Bay of Bengal) to spawn. The gut bacteria of paradise threadfin were characterized both physiologically and molecularly, and their antibiogram profile was formulated after collection from the Tetulia River, Bhola, Bangladesh. A total of 24 isolates were identified under the genera Bacillus, Salmonella, Brucella, Enterobacter, Citrobacter, Pseudomonas, and Kluyvera. Pseudomonas was one of the most dominant genera based on bacterial abundance in the gut of P. paradiseus. The majority of bacterial isolates showed maximum growth between 30 and 40 °C and at pH 8.5. All of the strains were multidrug resistant and showed up to 100% resistance to cefixime, penicillin, ampicillin, and neomycin. Strains of Enterobacter, Citrobacter, Kluyvera, and Pseudomonas showed 100% resistance to seven antibiotics. Bangla. J. Microbiol. 2025, Vol. 41, P: 1-6
Microbial cellulase is represented as biocatalysts due to their widespread applications in textile industries. As the cellulase from four fungal isolates can perform bio-stoning of denim fabrics, this enzyme may have the capability for the decolorization of textile dyes. This study evaluated the decolorization potential of four Aspergillus isolates, A. fumigatus AKAL1, A. oryzae AKAL4, A. flavus AKAL8, and A. flavus AKAL9, along with their crude cellulases. The crude cellulase having denim bio-stoning capability demonstrated decolorization of direct textile dyes, Dark Blue GL and Black VSF, with maximum decolorization percentages ranging from 50%-55% for both dyes. The fungal isolates effectively decolorized two commercial textile dyes. The maximum decolorization was achieved under static conditions. The optimal parameters for decolorization by the isolates were identified as 0.01% dye concentration, pH 7.0 for Dark Blue GL, pH 5.0 for Black VSF, incubation at 30°C for seven days, and dextrose as the carbon source. Results indicate that the four fungal isolates obtained in this study might be a potential source for textile dye decolorization. Bangla. J. Microbiol. 2025, Vol. 41, P: 1-8
With an emphasis on leguminous plants like Glycine max (soybean), Clitoria ternatea, and non-leguminous plants like Phaseolus lunatus, this study investigates the diversity of Plant Growth-Promoting Rhizobacteria (PGPR) isolated from the root nodules and rhizospheres of agricultural soil. Seventeen of the 42 isolates were chosen for further analysis. Isolates were screened through phenotypic characterization, presumptive identification, and evaluation of their plant growth-promoting (PGP) qualities. Amplification of the nitrogen[1]fixing nifH gene, the nodulation-inducing nodC gene, and the 16S rRNA were among the molecular investigations carried out. Three examined PGP features were present in 35% of the isolates, according to the results. From pH levels of 4.5 to 9, temperatures of 37oC to 40oC and salt concentrations of 1% or less, the isolates showed versatility in a variety of environmental circumstances. Resistant to high temperatures (40°C), slow-growing rhizobia (22%) were shown to be sensitive to high pH (9). Tilt and Tafgor pesticides had a more severe influence on PGP traits and development than Shadhin G and Semcup. The design and efficacy of biofertilizers, agro-economic progress, and sustainable agriculture are among the topics on which this qualitative study sheds important light. Bangladesh J Microbiol, Volume 40, Number 2, December 2023, pp 66-74
Various industries including the food and textile industries result in the release of azo dyes into the environment. These dyes are known to exert toxic effects on humans, animal and plants. Biological methods of azo dye bioremediation is a solution for the detoxification of azo dye in the environment. The present study was undertaken to isolate bacteria with potential for azo dye bioremediation. From five polluted environment samples, eight bacteria were isolated in azo dye supplemented Nutrient agar. Six isolates (75%, n=8) decolorized azo dye completely following 24 hours of incubation. The control tube with no bacterial inoculation remained blue, indicating that only microbial biotransformation processes were taking place. In each case, a blue-colored ring remained at the top, indicating the anoxic nature of the dye decolorization process. All isolates grew in presence of 400 ppm, 60% tolerated 600 ppm and 20% tolerated 800 ppm, whereas 1000ppm was inhibitory for growth of all isolates. Dead autoclaved cells of three representative isolates were tested for biosorption potential. Only one isolate turned the methylene blue supplemented nutrient broth colorless. This explains that this isolate was not metabolizing methylene blue rather it bound the dye to the cell structure. Two isolates did not show biosorption abilities indicating that their mechanism of bioremediation was enzymatic reduction. 16s rDNA sequencing identified two of the isolates as Lysinibacillus capsici and Stenotrophomonas muris. Bangladesh J Microbiol, Volume 40, Number 2, December 2023, pp 56-59
The use and search for antimicrobial drugs derived from plants have accelerated in recent years. The present study was aimed to determine the antimicrobial, antibiofilm and membrane stabilization activities of plant extracts. Crude extracts of four plants namely, Mikania scandens (L.), Mimosa pudica (L.), Murraya paniculata (L.), and Syzygium aromaticum (L.) were tested against eleven human pathogens including four biofilm producing bacterial strains Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and Staphylococcus aureus, and one fungal strain Candida albicans. The antimicrobial activities as well as minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the extracts were evaluated using disc diffusion and macro-broth dilution methods respectively. Among the plant extracts, ethanol extract of S. aromaticum exhibited the largest zone of inhibition 35 mm in diameter against Bacillus subtilis at 500 µg/disc concentrations. The lowest MIC (1000 µg/ml) and MBC (2500 µg/ml) were determined against P. aeruginosa with the same extract of S. aromaticum. In case of time kill assay, S. aromaticum extract showed the lowest optical density (OD600) 0.2 against E coli in 3h at MBC concentration. Moreover, the same extract of S. aromaticum displayed the strong antibiofilm activity, inhibiting 100% biofilm formation of E. coli at 2×MIC concentration. Furthermore, in vitro experiment was performed to evaluate membrane stabilization activity of plant extracts and S. aromaticum showed 100% activity in stabilizing cell membranes, preventing hemolysis of red blood cells. Therefore, this study provides valuable insight for designing antimicrobial products to efficiently eliminating human infections, and the plant extracts could be the potential antimicrobial agent. Bangladesh J Microbiol, Volume 40, Number 2, December 2023, pp 76-85
Textile dyeing industries are usually chastised for being big polluters due to the poisonous nature of most dyes, which endangers all kinds of life, including people. In this study, dye degrading bacteria were isolated from water and soil samples contaminated with textile dye taken from Batik palli in Narayanganj and the ability of five isolated bacteria including Staphylococcus saprophyticus, Bacillus pumilus, Micrococcus endophyticus, Pseudomonas mendocina, and Acinetobacter baumannii, to decolorize crystal violet (CV) dye was investigated. Among these, Bacillus pumilus decolorized 58% of CV at 250 ppm, while Staphylococcus saprophyticus decolorized 48% of CV, after 3 days of incubation at 37°C. We examined multiple temperature and pH conditions to determine the best parameters for CV dye decolorization. Bacillus pumilus boosted decolorization rates by 65.39% at 37°C and at pH 7.0, while Staphylococcus saprophyticus increased decolorization rates by 58.73%, at 37°C and at pH 5.0. Furthermore, extending the incubation period to 6 days enhanced decolorization rate in both isolates, with Bacillus pumilus increased from 58% to 65% and Staphylococcus saprophyticus increased from 48% to 58%. Nevertheless, the inclusion of co-substrates such glucose and yeast extract further boosting decolorization rate for both isolates, approximately tripling it. As a result, this study discovered indigenous bacteria capable of decolorizing CV dye, implying that they could be employed in the treatment of textile wastewater effluents. Bangladesh J Microbiol, Volume 40, Number 2, December 2023, pp 50-54
Aerobic methanotrophic bacteria maintain an unrivalled capability of utilizing methane as their sole carbon and energy source and have been retrieved from various environments. Phylogenetically, true aerobic thermoacidophilic methane oxidizers capable of growing below pH 3 have hitherto been associated only with the phylum Verrucomicrobia. In this report, the initial detection of a moderately thermoacidophilic Methylococcus-like Type Ib methanotroph of the class Gammaproteobacteria from an acidic thermal spring (50oC and pH 2.8) in the Yellowstone National Park, USA is presented. The isolate, termed YT-MC, was identified in a methane enrichment (55°C), which may represent a novel strain in the family Methylococcaceae Type Ib. The existence of this bacterium in the enrichments was demonstrated by the detection of pmoA gene, Southern blotting technique, phase-contrast, and electron microscopy. The coccus-typed cells showed tubular membranes instead of intracytoplasmic membrane systems (ICM). The soluble methane monooxygenase (sMMO) was not detected by PCR, indicating that the biotransformation of methane to methanol is oxidized by the particulate methane monooxygenase (pMMO). Moreover, YT-MC performs in a formerly undiscovered active biological methane sink in geothermal acidic environments, magnifying our knowledge of its ecological role in methane cycling, diversity, and coexistence of aerobic methanotrophy. Furthermore, the present study also reports the isolation and identification of an alphaproteobacterial heterotroph (strain YT-AC) and a verrucomicrobial methanotroph (strain YT-VM) from the same environment. Bangladesh J Microbiol, Volume 40, Number 2, December 2023, pp 86-94
Objectives:Biofilms are responsible for persistent infections and antimicrobial resistance. Pseudomonas aeruginosa was investigated with its ability to form biofilm by detecting genes responsible for producing biofilms and biofilm-specific antimicrobial resistance. The association between antibiotic resistance and biofilm was investigated. Methods:This cross-sectional study was conducted from July 2017 to December 2018. A total of 446 samples (infected burn, surgical wounds, and endotracheal aspirate) were collected from admitted patients of Dhaka Medical College and Hospital, Bangladesh. P. aeruginosa was isolated and identified by biochemical tests and polymerase chain reaction. Biofilm production by tissue culture plate method followed by detection of biofilm-producing genes (pqsA, pslA, pslD, pslH, pelA, lasR) and biofilm-specific antibiotic resistance genes (ndvB, PA1874, PA1876, PA1877) by polymerase chain reaction were done. Antibiotic susceptibility test was carried out by disk diffusion method; for colistin agar dilution method of minimal inhibitory concentration was followed. Results:Among 232 (52.02%) positive strains of P. aeruginosa, 24 (10.30%) produced biofilms in tissue culture plate. Among biofilm-producing genes, pqsA was the highest (79.17%). pslA and pelA were 70.83%, pslD 45.83%, pslH and lasR 37.5%. Among biofilm-specific antibiotic resistance genes, 16.67% were ndvB, and 8.33% were PA1874 and PA1877. Biofilm-forming strains were significantly resistant to colistin. Conclusions:Detection of biofilm-forming genes may be a good tool for the evaluation of biofilm production, which will help in prompt and better management of chronic or device-associated infections.
The occurrence of heavy metal-resistant bacteria in the environment acts as an indicator of heavy metal pollution. The impact of heavy metal contamination in co-selection and proliferation of antimicrobial[1]resistant bacteria is well-documented in existing literature. The present study aims to determine the occurrence of chromium-resistant bacteria (CRB) in poultry feces and to characterize their antimicrobial resistance and biofilm formation ability. 28 CRBs were isolated by inoculating samples on chromium-amended media. 6 of 28 isolates were resistant to a maximum of 1000 ppm chromium. Isolated CRBs also showed varying degrees of resistance to other heavy metals, including Cd, Ni, and Hg. Biofilm formation was observed in 67.8% isolates, of which 60.7% and 7.1% were weak and moderate biofilm former, respectively. All the isolates exhibited sensitivity to Gentamicin, Chloramphenicol, Imipenem, and Amikacin. Only one isolate was multi-drug resistant. In addition, all the isolates possessed chromate reductase gene that confirmed their chromium-reducing activity. Two isolates were identified as Bacillus altituidinis and Brevibcillus parabrevis on the basis of 16s rRNA analysis. Further estimation of chromium-reduction capacity and whole genome analysis will reveal their bioremediation potential. Bangladesh J Microbiol, Volume 40, Number 1, June 2023, pp 1-6
Antibiotic resistance among various microbial species is becoming a global threat to human health. MDR, or multidrug resistance, is an organism’s ability to tolerate the effects of many antimicrobial treatments. Klebsiella spp. is the major bacteria that causes a variety of illnesses, including urinary tract infections. The primary goal of this study is to look into the relationship between antibiotic resistance and Klebsiella spp. biofilm production. This study included 26 clinical isolates of Klebsiella spp. (n=26) collected from a tertiary hospital in Bangladesh. Isolates were obtained from blood, wound swabs, urine, and other sources. Following isolation and identification, ampicillin resistance was found in all MDR Klebsiella spp. isolates, followed by Cefotaxime (84.61%), Polymyxin B (84.61%), Amoxicillin (80.76%), Trimethoprim (69.23%), Doripenem (57.69%), Ciprofloxacin (57.69%), Imipenem (50.0%), Meropenem (38.46%), and Oxytetracycline (34.61%). Out of 26 clinical isolates, about 26.92% (n=7) were positive for the bla-NDM-1 gene. However, 15.8% of Klebsiella spp. (n = 4) isolates tested positive for the blaOXA-1 gene. There were no bla-KPC gene positives. Plasmid profile analysis revealed that 24 of 26 Klebsiella spp. isolates included numerous plasmids ranging in size from less than 2kb to more than 10kb. Biofilm formation found that 31% of samples were extremely positive for biofilm formation, 69% were medium biofilm formation, and (n=4) isolates were positive for biofilm resistance gene out of a total of 26 isolates. This study provides an early report on the widespread presence of carbapenem-resistant Klebsiella spp., demonstrating the need for intensive surveillance systems and research initiatives in Bangladesh to reflect the influence of multidrug resistance features in clinical isolates and their risks. Bangladesh J Microbiol, Volume 40, Number 1, June 2023, pp 25-32
The Dengue virus is a prevalent mosquito-borne disease, and its global incidence has been steadily increasing due to the favorable environmental conditions that promote mosquito breeding, primarily influenced by rising temperatures. Bangladesh has been particularly hard-hit by an intense and ongoing outbreak, resulting in a surge of cases and fatalities. Effective management of this disease necessitates the implementation of robust public health measures, including rigorous surveillance and early diagnosis. While serological tests are commonly employed in clinical diagnosis, molecular methods hold a critical role in identifying the specific Dengue virus strain, thereby contributing to a more comprehensive understanding of disease severity. This article serves as an extensive review, delving into various molecular testing techniques employed for both surveillance and clinical diagnosis. It offers valuable insights for research and clinical laboratories engaged in the detection of Dengue virus RNA in mosquitoes, environmental samples, and clinical specimens. The methods covered encompass a spectrum of approaches, including conventional PCR, isothermal amplification, real-time RT-PCR, Sanger sequencing, and whole-genome sequencing, providing a holistic overview of the available techniques. These methods play pivotal roles in clinical diagnosis, outbreak analysis, vector surveillance, and vaccine development. Furthermore, the article underscores the importance of integrating these techniques into existing healthcare systems, emphasizing their significance in ensuring precise dengue diagnostics to enhance the efficiency of disease management. These molecular methods are indispensable tools that contribute to accurate diagnosis, enable effective outbreak investigation, facilitate vector surveillance, and support vaccine preparation, thereby enhancing the overall management and control of dengue, ultimately working toward mitigating its impact on public health. Bangladesh J Microbiol, Volume 40, Number 1, June 2023, pp 41-49
Multidrug resistant (MDR) Pseudomonas aeruginosa is a threat to the patients having nosocomial infections as this pathogen increases the inpatients’ morbidity and mortality by slowing down the whole treatment process. The aim of this study was to evaluate multidrug resistant phenotypes among nosocomial strains of P. aeruginosa for analyzing their antibiotic susceptibility pattern. A total of 108 P. aeruginosa clinical isolates were recovered from various samples (pus, wound swab, urine, sputum, blood and tracheal aspirate) of patients with nosocomial infections. Antibiogram was performed by disc diffusion according to Kirby-Bauer method to study the antibiotic sensitivity pattern of the pathogen against 14 regularly used antibiotics (amikacin, aztreonam, ceftazidime, ceftriaxone, co-trimoxazole, ciprofloxacin, gentamicin, levofloxacin, meropenem, netilmicin, doxycycline, amoxicillin/clavulanic acid, piperacillin/tazobactam, and tigecycline) in Bangladesh. The overall frequency of drug resistance was found to be very high (53.7% - 98.1%) to all of the anti-pseudomonal drugs tested. Resistance of P. aeruginosa strains against piperacillin-tazobactam was significantly less (53.7%) as compared to other thirteen antibiotics. However, isolates showed highest resistance (98.1%) to aztreonam. Next in order of resistance were doxycycline (95.4%), ceftriaxone (94.4%), amoxiclav (93.5%), and the others. The present study suggests that regularly used medications can no longer be utilized as first line therapies for suspected pseudomonad infections. This study claims for urgent epidemiological monitoring of the MDR P. aeruginosa strains in all hospitals of Bangladesh to prevent rapid dissemination of this opportunistic pathogen. Bangladesh J Microbiol, Volume 40, Number 1, June 2023, pp 7-13
Malate Dehydrogenase (MDH) stands as a pivotal enzyme crucial for cellular energy metabolism, orchestrating the conversion of malate to oxaloacetate in both prokaryotic and eukaryotic organisms. This study delves into the evolutionary trajectories of MDH1 (cytoplasmic) and MDH2 (mitochondrial), offering substantial evidence supporting the archaebacterial origin of eukaryotes. The dataset spans nine groups, encompassing human MDH1 and MDH2, mammalian MDH1 and MDH2, amphibian MDH2, arthropod MDH2, amoeba MDH1, archaea, and bacteria. Protein BLAST analysis revealed significant sequence homology in mammalian MDH1, particularly among primates, underlining a close evolutionary connection. Conversely, lower eukaryotes, including amoeba, arthropods, and amphibians, exhibited marked divergence from human MDH1 and MDH2. Phylogenetic analysis unveils distinct clusters for MDH1 and MDH2, accentuating significant genetic diversity between mitochondrial and cytoplasmic MDH enzymes. Prokaryotic MDH sequences cluster with human mitochondrial MDH2, while MDH1 forms a separate cluster. Staphylococcus MDH aligns with archaeal MDH, emphasizing the diversity within bacterial MDH evolution. Protein variability analysis indicates noteworthy divergence of human MDH1 from prokaryotic MDH, while MDH2 displays comparatively lower divergence. Pairwise evolutionary divergence analysis sheds light on complex relationships among MDH protein sequences. Human MDH1 shows close evolutionary ties to mammalian MDH1, whereas MDH2 exhibits a unique pattern, aligning closely with mammalian MDH2, arthropods, and amphibians. Furthermore, MDH2 demonstrates closer proximity to bacterial MDH, supporting a bacterial origin of mitochondrial MDH. In contrast, MDH1 displays less divergence to archaeal MDH than its bacterial counterpart, endorsing an archaeal origin for cytoplasmic MDH. In conclusion, this study provides compelling support for the archaebacterial origin of eukaryotes, suggesting a bacterial endosymbiont within an archaeal host that evolved into mitochondria. It contributes valuable insights into MDH evolution, unraveling the intricate relationships and unique adaptations shaping the evolutionary history of eukaryotic cells. Bangladesh J Microbiol, Volume 40, Number 1, June 2023, pp 15-24
