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Frontiers in Clinical Diabetes and... 2023Gestational diabetes mellitus (GDM) is one of the most frequent endocrine conditions during pregnancy. GDM is linked to adverse pregnancy outcomes and has implications... (Review)
Review
Gestational diabetes mellitus (GDM) is one of the most frequent endocrine conditions during pregnancy. GDM is linked to adverse pregnancy outcomes and has implications for maternal health. Studies have demonstrated the link between pathogenic periodontal bacteria, glycemic control, and the risk of diabetes. The objective of the current study is to perform a mini-review of the available literature on the potential changes in the oral microbiota of women with GDM. The review was conducted by two independent reviewers (LLF and JDC). Indexed electronic databases (PubMed/Medline, Cochrane Library, Web of Science, and Scopus) were searched, including articles published in English and Portuguese. A manual search was also performed to identify related articles. The oral microbial community of pregnant women with GDM is unique from that of healthy pregnant women. The majority of the alterations found in the oral microbiota of women with GDM point to a pro-inflammatory environment with high levels of bacteria associated with periodontitis (, anaerobic bacteria) and a depletion of bacteria associated with periodontal health maintenance (Firmicutes, More well-designed studies differentiating between pregnant women with good oral health and those with periodontitis are needed to ascertain which differences are due to GDM or periodontitis.
PubMed: 36993820
DOI: 10.3389/fcdhc.2023.1120920 -
Frontiers in Bioengineering and... 2020In the last years several human commensals have emerged from the gut microbiota studies as potential probiotics or therapeutic agents. Strains of human gut inhabitants... (Review)
Review
In the last years several human commensals have emerged from the gut microbiota studies as potential probiotics or therapeutic agents. Strains of human gut inhabitants such as , or have shown several interesting bioactivities and are thus currently being considered as food supplements or as live biotherapeutics, as is already the case with other human commensals such as bifidobacteria. The large-scale use of these bacteria will pose many challenges and drawbacks mainly because they are quite sensitive to oxygen and/or very difficult to cultivate. This review highlights the properties of some of the most promising human commensals bacteria and summarizes the most up-to-date knowledge on their potential health effects. A comprehensive outlook on the potential strategies currently employed and/or available to produce, stabilize, and deliver these microorganisms is also presented.
PubMed: 32582673
DOI: 10.3389/fbioe.2020.00550 -
Frontiers in Microbiology 2021Anaerobic bacteria ferment carbohydrates and amino acids to obtain energy for growth. Due to the absence of oxygen and other inorganic electron acceptors, the substrate... (Review)
Review
Anaerobic bacteria ferment carbohydrates and amino acids to obtain energy for growth. Due to the absence of oxygen and other inorganic electron acceptors, the substrate of a fermentation has to serve as electron donor as well as acceptor, which results in low free energies as compared to that of aerobic oxidations. Until about 10 years ago, anaerobes were thought to exclusively use substrate level phosphorylation (SLP), by which only part of the available energy could be conserved. Therefore, anaerobes were regarded as unproductive and inefficient energy conservers. The discovery of electrochemical Na gradients generated by biotin-dependent decarboxylations or by reduction of NAD with ferredoxin changed this view. Reduced ferredoxin is provided by oxidative decarboxylation of 2-oxoacids and the recently discovered flavin based electron bifurcation (FBEB). In this review, the two different fermentation pathways of glutamate to ammonia, CO, acetate, butyrate and H via 3-methylaspartate or via 2-hydroxyglutarate by members of the are discussed as prototypical examples in which all processes characteristic for fermentations occur. Though the fermentations proceed on two entirely different pathways, the maximum theoretical amount of ATP is conserved in each pathway. The occurrence of the 3-methylaspartate pathway in clostridia from soil and the 2-hydroxyglutarate pathway in the human microbiome of the large intestine is traced back to the oxygen-sensitivity of the radical enzymes. The coenzyme B-dependent glutamate mutase in the 3-methylaspartate pathway tolerates oxygen, whereas 2-hydroxyglutaryl-CoA dehydratase is extremely oxygen-sensitive and can only survive in the gut, where the combustion of butyrate produced by the microbiome consumes the oxygen and provides a strict anaerobic environment. Examples of coenzyme B-dependent eliminases are given, which in the gut are replaced by simpler extremely oxygen sensitive glycyl radical enzymes.
PubMed: 34589068
DOI: 10.3389/fmicb.2021.703525 -
Current Opinion in Microbiology Oct 2021A central goal of microbiome research is to understand the factors that balance gut-associated microbial communities, thereby creating longitudinal and cross-sectional... (Review)
Review
A central goal of microbiome research is to understand the factors that balance gut-associated microbial communities, thereby creating longitudinal and cross-sectional heterogeneity in their composition and density. Whereas the diet dictates taxa dominance, microbial communities are linked intimately to host physiology through digestive and absorptive functions that generate longitudinal heterogeneity in nutrient availability. Additionally, the host differentially controls the access to electron acceptors along the longitudinal axis of the intestine to drive the development of microbial communities that are dominated by facultatively anaerobic bacteria in the small intestine or obligately anaerobic bacteria in the large intestine. By secreting mucus and antimicrobials, the host further constructs microhabitats that generate cross-sectional heterogeneity in the colonic microbiota composition. Here we will review how understanding the host factors involved in generating longitudinal and cross-sectional microbiota heterogeneity helps define physiological states that are characteristic of or appropriate to a homeostatic microbiome.
Topics: Cross-Sectional Studies; Diet; Gastrointestinal Microbiome; Microbiota
PubMed: 34428628
DOI: 10.1016/j.mib.2021.08.004 -
Antibiotics (Basel, Switzerland) Dec 2022Anaerobes play an important role in clinically relevant infections and resistance is increasing worldwide. We tested 120 rare anaerobic isolates belonging to 16 genera...
Anaerobes play an important role in clinically relevant infections and resistance is increasing worldwide. We tested 120 rare anaerobic isolates belonging to 16 genera for antimicrobial resistance using the agar dilution method and compared those results to the time-saving E-test method. The susceptibility data for 12 antimicrobial substances (benzylpenicillin, ampicillin/sulbactam, piperacillin/tazobactam, imipenem, meropenem, cefoxitin, metronidazole, moxifloxacin, clindamycin, doxycycline, tigecycline, eravacycline) were collected. Susceptibility testing showed low resistance to β-lactam/β-lactamase inhibitor combinations and no resistance to carbapenems and tigecycline. We observed moderate to high rates of resistance to moxifloxacin and clindamycin which differed depending on the methodology used. The essential and categorical agreement was over 90% for ampicillin/sulbactam, meropenem, moxifloxacin, and tigecycline. For metronidazole and clindamycin, the essential agreement was below 90% but the categorical agreement was near or above 90%. Penicillin presented with the lowest categorical agreement of 86.7% and a very high very major error rate of 13.3%. The resistance rates reported in this study are concerning and show the importance of routine susceptibility testing. Further investigations are necessary to determine the reason for high error rates and how to improve susceptibility testing of fastidious anaerobes.
PubMed: 36671264
DOI: 10.3390/antibiotics12010063 -
Antibiotics (Basel, Switzerland) May 2023Anaerobic Gram-negative bacteria (AGNB) play a significant role as both pathogens and essential members of the human microbiota. Despite their clinical importance, there...
BACKGROUND
Anaerobic Gram-negative bacteria (AGNB) play a significant role as both pathogens and essential members of the human microbiota. Despite their clinical importance, there remains limited understanding regarding their antimicrobial resistance (AMR) patterns. This knowledge gap poses challenges in effectively managing AGNB-associated infections, as empirical treatment approaches may not adequately address the evolving resistance landscape. To bridge this research gap, we conducted a comprehensive study aimed at exploring the role of human AGNB as a reservoir of AMR. This can provide valuable insights for the prevention and management of anaerobic infections.
METHODS
We studied the prevalence of AMR and AMR determinants conferring resistance to metronidazole (), imipenem (), piperacillin-tazobactam (), cefoxitin (), clindamycin (), chloramphenicol () and mobile genetic elements (MGEs) such as and 1186 associated with the and gene expression. These parameters were studied in spp., spp., spp., spp., spp., and other clinical AGNB.
RESULTS
Resistance to metronidazole, clindamycin, imipenem, piperacillin-tazobactam, cefoxitin and chloramphenicol was 29%, 33.5%, 0.5%, 27.5%, 26.5% and 0%, respectively. The presence of resistance genes, viz., , , , , was detected in 24%, 33.5%, 10%, 9.5%, 21.5% isolates, respectively. None of the tested isolates showed the presence of a gene and MGEs, viz., and IS. The highest resistance to all antimicrobial agents was exhibited by spp. The association between resistant phenotypes and genotypes was complete in clindamycin, as all clindamycin-resistant isolates showed the presence of gene, and none of the susceptible strains harbored this gene; similarly, all isolates were chloramphenicol-susceptible and also lacked the gene, whereas the association was low among imipenem and piperacillin-tazobactam. Metronidazole and imipenem resistance was seen to be dependent on insertion sequences for the expression of AMR genes. A constrained co-existence of and gene in species was seen. Based on the absence and presence of the gene, we divided into two categories, Division I (72.6%) and Division II (27.3%), respectively.
CONCLUSION
AGNB acts as a reservoir of specific AMR genes, which may pose a threat to other anaerobes due to functional compatibility and acquisition of these genes. Thus, AST-complying standard guidelines must be performed periodically to monitor the local and institutional susceptibility trends, and rational therapeutic strategies must be adopted to direct empirical management.
PubMed: 37237845
DOI: 10.3390/antibiotics12050942 -
International Journal of Molecular... Jul 2021Microbial biodegradation is one of the acceptable technologies to remediate and control the pollution by polycyclic aromatic hydrocarbon (PAH). Several bacteria, fungi,... (Review)
Review
Microbial biodegradation is one of the acceptable technologies to remediate and control the pollution by polycyclic aromatic hydrocarbon (PAH). Several bacteria, fungi, and cyanobacteria strains have been isolated and used for bioremediation purpose. This review paper is intended to provide key information on the various steps and actors involved in the bacterial and fungal aerobic and anaerobic degradation of pyrene, a high molecular weight PAH, including catabolic genes and enzymes, in order to expand our understanding on pyrene degradation. The aerobic degradation pathway by PRY-1 and sp. KMS and the anaerobic one, by the facultative bacteria anaerobe sp. JP1 and sp. LZ6 are reviewed and presented, to describe the complete and integrated degradation mechanism pathway of pyrene. The different microbial strains with the ability to degrade pyrene are listed, and the degradation of pyrene by consortium is also discussed. The future studies on the anaerobic degradation of pyrene would be a great initiative to understand and address the degradation mechanism pathway, since, although some strains are identified to degrade pyrene in reduced or total absence of oxygen, the degradation pathway of more than 90% remains unclear and incomplete. Additionally, the present review recommends the use of the combination of various strains of anaerobic fungi and a fungi consortium and anaerobic bacteria to achieve maximum efficiency of the pyrene biodegradation mechanism.
Topics: Klebsiella; Microbial Consortia; Mycobacterium; Oxygen; Pseudomonas; Pyrenes
PubMed: 34360967
DOI: 10.3390/ijms22158202 -
Journal of Medical Microbiology Mar 2024There is growing evidence that altered microbiota abundance of a range of specific anaerobic bacteria are associated with cancer, including spp., spp., spp., spp.,... (Review)
Review
There is growing evidence that altered microbiota abundance of a range of specific anaerobic bacteria are associated with cancer, including spp., spp., spp., spp., spp., spp spp and spp. linked to multiple cancer types. In this review we explore these pathogenic associations. The mechanisms by which bacteria are known or predicted to interact with human cells are reviewed and we present an overview of the interlinked mechanisms and hypotheses of how multiple intracellular anaerobic bacterial pathogens may act together to cause host cell and tissue microenvironment changes associated with carcinogenesis and cancer cell invasion. These include combined effects on changes in cell signalling, DNA damage, cellular metabolism and immune evasion. Strategies for early detection and eradication of anaerobic cancer-associated bacterial pathogens that may prevent cancer progression are proposed.
Topics: Humans; Bacteria, Anaerobic; Carcinogenesis; Immune Evasion; Porphyromonas; Signal Transduction; Tumor Microenvironment
PubMed: 38535967
DOI: 10.1099/jmm.0.001817 -
Applied Microbiology and Biotechnology Jun 2020Lignocellulose is a widely available renewable carbon source and a promising feedstock for the production of various chemicals in biorefineries. However, its... (Review)
Review
Lignocellulose is a widely available renewable carbon source and a promising feedstock for the production of various chemicals in biorefineries. However, its recalcitrant nature is a major hurdle that must be overcome to enable economic conversion processes. Deconstruction of lignocellulose is part of the global carbon cycle, and efficient microbial degradation systems have evolved that might serve as models to improve commercial conversion processes. Biofilms-matrix encased, spatially organized clusters of microbial cells and the predominating lifestyle in nature-have been recognized for their essential role in the degradation of cellulose in nature, e.g., in soils or in the digestive tracts of ruminant animals. Cellulolytic biofilms allow for a high concentration of enzymes at the boundary layer between the solid substrate and the liquid phase and the more complete capture of hydrolysis products directly at the hydrolysis site, which is energetically favorable. Furthermore, enhanced expression of genes for carbohydrate active enzymes as a response to the attachment on solid substrate has been demonstrated for cellulolytic aerobic fungi and anerobic bacteria. In natural multispecies biofilms, the vicinity of different microbial species allows the creation of efficient food webs and synergistic interactions thereby, e.g., avoiding the accumulation of inhibiting metabolites. In this review, these topics are discussed and attempts to realize the benefits of biofilms in targeted applications such as the consolidated bioprocessing of lignocellulose are highlighted. KEY POINTS: Multispecies biofilms enable efficient lignocellulose destruction in the biosphere. Cellulose degradation by anaerobic bacteria often occurs by monolayered biofilms. Fungal biofilms immobilize enzymes and substrates in an external digestion system. Surface attached cultures typically show higher expression of cellulolytic enzymes.
Topics: Aerobiosis; Anaerobiosis; Bacteria, Anaerobic; Biofilms; Cellulose; Fungi; Hydrolysis; Lignin
PubMed: 32337627
DOI: 10.1007/s00253-020-10595-y -
Nature Reviews. Microbiology Dec 2021The defining trait of obligate anaerobes is that oxygen blocks their growth, yet the underlying mechanisms are unclear. A popular hypothesis was that these... (Review)
Review
The defining trait of obligate anaerobes is that oxygen blocks their growth, yet the underlying mechanisms are unclear. A popular hypothesis was that these microorganisms failed to evolve defences to protect themselves from reactive oxygen species (ROS) such as superoxide and hydrogen peroxide, and that this failure is what prevents their expansion to oxic habitats. However, studies reveal that anaerobes actually wield most of the same defences that aerobes possess, and many of them have the capacity to tolerate substantial levels of oxygen. Therefore, to understand the structures and real-world dynamics of microbial communities, investigators have examined how anaerobes such as Bacteroides, Desulfovibrio, Pyrococcus and Clostridium spp. struggle and cope with oxygen. The hypoxic environments in which these organisms dwell - including the mammalian gut, sulfur vents and deep sediments - experience episodic oxygenation. In this Review, we explore the molecular mechanisms by which oxygen impairs anaerobes and the degree to which bacteria protect their metabolic pathways from it. The emergent view of anaerobiosis is that optimal strategies of anaerobic metabolism depend upon radical chemistry and low-potential metal centres. Such catalytic sites are intrinsically vulnerable to direct poisoning by molecular oxygen and ROS. Observations suggest that anaerobes have evolved tactics that either minimize the extent to which oxygen disrupts their metabolism or restore function shortly after the stress has dissipated.
Topics: Anaerobiosis; Bacteria, Anaerobic; Bacteroides; Clostridium; Desulfovibrio; Hydrogen Peroxide; Oxygen; Pyrococcus; Reactive Oxygen Species; Superoxides
PubMed: 34183820
DOI: 10.1038/s41579-021-00583-y