The search for nature-based tools to enhance bioremediation is essential for the sustainable restoration of contaminated ecosystems. Humic acid (HA) is an important component of organic matter in ...soil and water, but its effect on the microbial degradation of organic pollutants remains unclear. In this study, the biodegradation of pyrene by Mycobacterium sp. NJS-1 with and without HA was investigated. Only around 10.5% of pyrene was biodegraded in the pyrene treatment alone, whereas the addition of HA significantly enhanced biodegradation to the point where over 90% of pyrene was biodegraded. The production of 4,5-dihydropyrene-4,5-diol and phenanthrene-3,4-diol indicated the metabolic pathway via attacking of 4,5-positions of pyrene. Interestingly, 1,2-dimethoxypyrene was detected with the addition of HA, suggesting that HA induced a new ring-opening pathway involving the attack on the 1,2-positions of pyrene. The addition of HA first induced protein self-cleavage behavior with a significant increase in phenylalanine, tyrosine, and tryptophan containing large numbers of COO− groups. Furthermore, it altered the intracellular and extracellular ultrastructure of bacterial cells, promoting their growth in size and number as well as reducing the space between them. Overall, HA increased the ring-opening positions of pyrene and facilitated its interaction with bacterial cells, thus improving its biodegradability. Building upon the findings of this study to further research is conducive to the sustainable solution of environmental pollution.
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•The presence of HA promoted pyrene degradation by Mycobacterium sp. NJS-1.•Phenanthrene-3,4-diol and 1,2-dimethoxypyrene were detected.•HA induced distinct morphologies in bacteria cells.•Band shifting indicated the complexation of bacterial cells with HA.
Microbial fuel cells (MFCs) have been tentatively applied for wastewater treatment, but the presence of nitrogen, especially nitrate, induces performance instability by changing the composition of ...functional biofilms. A novel denitrifying exoelectrogenic strain EB-1, capable of simultaneous denitrification and electricity generation and affiliated with
sp., was isolated from the anodic biofilm of MFCs fed with nitrate containing medium. Polarization curves and cyclic voltammetry showed that strain EB-1 could generate electricity through a direct electron transfer mechanism with a maximum power density of 0.84 ± 0.05 W m
. Additionally, anodic denitrification, as a concurrent metabolism, was demonstrated with an efficient removal rate of 0.66 ± 0.01 kg N m
d
at a COD/N ratio of 3.5 ± 0.3. Importantly, voltage output was not negatively influenced by nitrate, indicating that the concurrent process of nitrate removal and electricity generation was a limitation of the electron donor rather than an inhibition of the system. Furthermore, various organic materials were successfully utilized as anode donors for strain EB-1, and demonstrated the exciting performances in terms of simultaneous denitrification and electricity generation.
sp. EB-1 thus expands the diversity of exoelectrogens and contributes to the potential applications of MFC for simultaneous energy recovery and wastewater treatment.
Protein engineering based on structure homology holds the potential to engineer steroid-transforming enzymes on demand. Based on the genome sequencing analysis of industrial Mycobacterium strain ...HGMS2 to produce 4-androstene-3,17-dione (4-AD), three hypothetical proteins were predicted as putative Δ5–3-ketosteroid isomerases (KSIs) to catalyze an intramolecular proton transfer involving the transformation of 5-androstene-3,17-dione (5-AD) into 4-AD, which were defined as mKSI228, mKSI291 and mKSI753. Activity assays indicated that mKSI228 and mKSI291 exhibited weak activity, as low as 0.7% and 1.5%, respectively, of a well-studied and highly active KSI from Pseudomonas putida KSI (pKSI), while mKSI753 had no activity similar to Mycobacterium tuberculosis KSI (mtKSI). Although the 3D structures of the putative mKSIs were homologous to pKSI, their amino acid sequences were significantly different from those of pKSI and tKSI. Thus, by use of these two KSIs as homology models, we were able to convert the low-active mKSI291 into a high-active active KSI by site-directed mutagenesis. On the other hand, an X-ray crystallographic structure of mKSI291 identified a water molecule in its active site. This unique water molecule might function as a bridge to connect Ser-OH, Tyr57-OH and C3O of the intermediate form a hydrogen-bonding network that was responsible for its weak activity, compared with that of mtKSI. Our results not only demonstrated the use of a protein engineering approach to understanding KSI catalytic mechanism, but also provided an example for engineering the catalytic active sites and gaining a functional enzyme based on homologous structures.
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•Protein design based on structure homology holds the potential to engineer steroid-transforming enzymes on demand.•Three hypothetical proteins from the industrial Mycobacterium HGMS2 for the production of 4-androstene-3,17-dione (4-AD) are structurally homologous to a highly-active KSI from Pseudomonas putida KSI (pKSI).•In this work, a pKSI-like active site was reconstructed step-by-step on one hypothetical protein mKSI291 which had weak KSI activity using protein engineering strategy.•On the other hand, an X-ray crystallographic structure of mKSI291 identified a water molecule in its active site that might play an important role in its weak activity.•Thus, our work demonstrates a feasibility to construct active enzymes based on homology structures.
Mycobacterium sp. and Haplosporidium pinnae constitute invasive parasite species of bivalves, reported for the first time in the present study in the Aegean Sea and Thermaikos Gulf, respectively. ...During the last years, the endangered fan mussel (Pinna nobilis) experienced several mortality events in the Mediterranean Sea that caused deaths to 90% or more of their populations and have been attributed to infections by these pathogens. In Greece, two mass mortality events have been recently reported, namely in the Gulf of Kalloni and in Limnos island. In the present study we investigated the presence of both pathogens in P. nobilis from these marine areas as well as from Thermaikos Gulf using both histopathological microscopy and molecular markers. The detected parasite DNA was further quantified in the three populations utilizing a real time qPCR. Histopathological results indicated the presence of a Mycobacterium species alongside with the existence of the Haplosporidian parasite, which was identified in all mortality events in the Mediterranean Sea. The parasite was present in different phases mostly on the digestive gland epithelium. Phylogenetic analysis confirmed the taxonomy of the Haplosporidian parasite as the recently described Haplosporidium pinnae, whereas it failed to identify the Mycobacteria parasite at species level. While Mycobacterium sp. was detected in all examined specimens, H. pinnae was not detected in all diseased fan mussels. Interestingly, monitoring of P. nobilis population from Thermaikos Gulf, an estuary of extremely high importance for bivalve production, revealed the presence of both pathogens in a few specimens in higher quantity but with no symptoms of the disease. Besides, all the specimens from Thermaikos Gulf had inflammatory responses similarly to moribund specimens from mortality events.
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•The invasive parasite Mycobacterium sp. is detected for the first time in bivalves in the Aegean Sea.•Haplosporidium pinnae infection is recorded for the first time in Pinna nobilis populations from Thermaikos Gulf..•Despite the higher infection in Pinna nobilis from Thermaikos, no symptoms of the diseases were observed in these specimens.•Phylogenetic analysis demonstrated that both parasites invaded in the Aegean Sea from the Western Mediterranean.
•Coexpression of vgb and mceG enhances the growth and productivity of Mycobacterium.•Coexpression reduces intracellular ROS levels and increases cell viability.•Bagasse is an excellent immobilization ...carrier for recombinant bacteria.•Immobilized culture increases the substrate tolerance of recombinant bacteria.•Production increased by 1.82 times using immobilized repeated batch fermentation.
Androstenone production is limited by low-efficiency substrate transport and dissolved oxygen levels during fermentation. In this study, the coexpression of the optimized Vitreoscilla hemoglobin (VHb) and sterol transporter ATPase (MceG) genes in Mycobacterium sp. LZ2 (Msp) was investigated to alleviate dissolved oxygen and mass transfer limitations. Results revealed that Msp-vgb/mceG effectively improved the growth, production, and adaptation to dissolved oxygen compared with those of Msp. The increased catalase activity and reduced intracellular ROS levels enhanced cell viability and promoted transcription of genes critical for phytosterol metabolism. Bagasse as an immobilization carrier increased the productivity of Msp-vgb/mceG by 56%. Immobilized repeat batch fermentation reduced the biotransformation period from 60 days to 37 days and improved the productivity from 0.039 g/L/h to 0.069 g/L/h. To the best of our knowledge, this work is the first study on the immobilization of recombinant mycobacteria on bagasse for androstenone production.
This study aimed to evaluate the to evaluate the occurrence rate of bovine brucellosis and tuberculosis in dairy herds of Acre State, Brazil. The survey was performed on 487 lactating cows ...distributed across 27 farms in seven cities from June 2018 to February 2019. Farms were selected according to the following criteria: volume of milk production (150 L/day), distance to an urban perimeter (43 km), and time of dairy activity (12 years). For the diagnosis of brucellosis, buffered acidified plate antigen (BAPA) and complement fixation (CF) tests were used. Among the investigated animals, the occurrence rates for brucellosis and tuberculosis were 1.88% (9/487) and 1.23% (6/487), respectively; among the investigated farms, 11.11% (3/27) and 22.2% (6/27) had livestock diagnosed as positive for brucellosis and tuberculosis, respectively. The farms with tuberculosis-positive cattle possessed some common features with respect to herd size. These farms had considerable herd sizes, which were reared extensively in pastures shared with other susceptible or pathogen-carrying animals. In conclusion, the occurrence rate of bovine brucellosis and tuberculosis in dairy herds from Acre state is, in general, lower than that observed in other states of Brazil. Nevertheless, there is an urgent need for developing strategies to control and eradicate both diseases to prevent eventual outbreaks and pathogen dissemination.
Abstract Natural products have been touted as important tools because of their vast potential for the development of compounds with antimicrobial activity and the possible inhibitory activity and/or ...adjuvant resistance mechanisms. Propolis has been empirically used for many years for the treatment of diseases, mainly due to its antioxidant, anti inflammatory and antimicrobial activities. This study aimed to evaluate the in vitro antimycobacterial activity of the ethanol extract of propolis alone and in combination with rifampicin (RIF), amikacin (AMI) and ciprofloxacin (CIP). The ethanol extract of propolis showed antibacterial activity against Mycobacterium chelonae and M. kansasii and was capable of increasing AMI, RIF and CIP activity in combination. On the other hand, compared to M. absecessus, M. fortuitum and M. avium, the extract was not active at 200 µg/mL and did not show pronounced adjuvant capacity when evaluated in association with the drugs. Based on these results, it can be concluded that the ethanol extract of propolis could be an alternative in the development of new drugs and can be used complementary with the current mycobacteriosis treatment.
Resumo Os produtos naturais têm sido apontados como ferramentas importantes devido ao seu vasto potencial para o desenvolvimento de compostos com atividade antimicrobiana e a possível atividade inibitória e/ou adjuvante de mecanismos de resistência. O própolis é utilizado empiricamente há muitos anos no tratamento de doenças, principalmente devido às suas atividades antioxidantes, anti-inflamatórias e antimicrobianas. Este estudo teve como objetivo avaliar a atividade antimicobacteriana in vitro do extrato etanólico de própolis isoladamente e em associação com rifampicina (RIF), amicacina (AMI) e ciprofloxacina (CIP). O extrato etanólico de própolis mostrou atividade antibacteriana frente Mycobacterium chelonae e M. kansasii e foi capaz de aumentar a atividade de AMI, RIF e CIP em associação. Por outro lado, frente a M. absecessus, M. fortuitum e M. avium, o extrato não foi ativo a 200 µg/mL e não apresentou capacidade adjuvante pronunciada quando avaliado em associação com os fármacos. Com base nesses resultados, pode-se concluir que o extrato etanólico de própolis pode ser uma alternativa no desenvolvimento de novos fármacos e pode ser utilizado complementarmente com o atual tratamento das micobacterioses.
To determine the presence of Mycobacterium sp in captive wild birds in the state of Jalisco, Mexico, an experimental study was carried out in private hatcheries of three municipalities in the state ...of Jalisco, covering Guadalajara, Tesistan, and Tonala to identify the presence of alcohol-acid resistant bacilli (ABB) in stool samples stained with the use of the Ziehl-Neelsen stain, stool samples were taken from 76 birds under captive conditions. Of the 33 birds analyzed in the municipality of Guadalajara, 4 tested positive for Mycobacterium sp., Giving 0.12 % positivism in this municipality, while, in Tesistan, of 21 birds analyzed, only one specimen tested positive for Mycobacterium sp., Giving 0.4 % positivism. In the municipality of Tonala, a positive specimen was found out of 22 birds analyzed, giving 0.45 % of bird’s positive for Mycobacterium sp. Of the 76 birds analyzed, 0.7 % were positive for Mycobacterium sp. Species such as Eupsittula canicularis, Amazona autumnalis, Ara militaris, Alopochen aegyptica, and Pavo cristatus tested positive for Mycobacterium sp. This work contributes to documenting the cases of Mycobacterium sp., In captive wild birds to take measures that guarantee the health of wild birds.
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