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Journal of Inorganic Biochemistry Sep 2021Selenium (Se) respiration in bacteria was revealed for the first time at the end of 1980s. Although thermodynamically-favorable, energy-dense and documented in... (Review)
Review
Selenium (Se) respiration in bacteria was revealed for the first time at the end of 1980s. Although thermodynamically-favorable, energy-dense and documented in phylogenetically-diverse bacteria, this metabolic process appears to be accompanied by a number of challenges and numerous unanswered questions. Selenium oxyanions, SeO and SeO, are reduced to elemental Se (Se) through anaerobic respiration, the end product being solid and displaying a considerable size (up to 500 nm) at the bacterial scale. Compared to other electron acceptors used in anaerobic respiration (e.g. N, S, Fe, Mn, and As), Se is one of the few elements whose end product is solid. Furthermore, unlike other known bacterial intracellular accumulations such as volutin (inorganic polyphosphate), S, glycogen or magnetite, Se has not been shown to play a nutritional or ecological role for its host. In the context of anaerobic respiration of Se oxyanions, biogenic Se appears to be a by-product, a waste that needs proper handling, and this raises the question of the evolutionary implications of this process. Why would bacteria use a respiratory substrate that is useful, in the first place, and then highly detrimental? Interestingly, in certain artificial ecosystems (e.g. upflow bioreactors) Se might help bacterial cells to increase their density and buoyancy and thus avoid biomass wash-out, ensuring survival. This review article provides an in-depth analysis of selenium respiration (model selenium respiring bacteria, thermodynamics, respiratory enzymes, and genetic determinants), complemented by an extensive discussion about the evolutionary implications and the properties of biogenic Se using published and original/unpublished results.
Topics: Bacteria, Anaerobic; Bacterial Proteins; Cell Respiration; Oxidoreductases; Selenium; Thermodynamics
PubMed: 34118782
DOI: 10.1016/j.jinorgbio.2021.111509 -
International Journal of Biological... Jan 2021Economic production of lignocellulose degrading enzymes for biofuel industries is of considerable interest to the biotechnology community. While these enzymes are widely... (Review)
Review
Economic production of lignocellulose degrading enzymes for biofuel industries is of considerable interest to the biotechnology community. While these enzymes are widely distributed in fungi, their industrial production from other sources, particularly by thermophilic anaerobic bacteria (growth T ≥ 60 °C), is an emerging field. Thermophilic anaerobic bacteria produce a large number of lignocellulolytic enzymes having unique structural features and employ different schemes for biomass degradation, which can be classified into four systems namely; 'free enzyme system', 'cell anchored enzymes', 'complex cellulosome system', and 'multifunctional multimodular enzyme system'. Such enzymes exhibit high specific activity and have a natural ability to withstand harsh bioprocessing conditions. However, achieving a higher production of these thermostable enzymes at current bioprocessing targets is challenging. In this review, the research opportunities for these distinct enzyme systems in the biofuel industry and the associated technological challenges are discussed. The current status of research findings is highlighted along with a detailed description of the categorization of the different enzyme production schemes. It is anticipated that high temperature-based bioprocessing will become an integral part of sustainable bioenergy production in the near future.
Topics: Bacteria, Anaerobic; Bacterial Proteins; Biomass; Enzyme Stability; Enzymes; Lignin; Thermodynamics
PubMed: 33309672
DOI: 10.1016/j.ijbiomac.2020.12.004 -
Applied Biochemistry and Biotechnology Aug 1994New obligately anaerobic bacteria are being discovered at an accelerating rate and it is becoming very evident that the diversity of anoxic biotransformations has been... (Review)
Review
New obligately anaerobic bacteria are being discovered at an accelerating rate and it is becoming very evident that the diversity of anoxic biotransformations has been greatly underestimated. Furthermore, among contemporary anaerobes there are many that thrive in extreme environments including, for example, an impressive array of both archaebacterial and eubacterial hyperthermophiles. Free energy for growth and reproduction may be conserved not only via fermentations but also by anoxygenic photophosphorylation and other modes of creating transmembrane proton potential. Thus forms of anaerobic respiration in which various inorganic oxidants (or indeed carbon dioxide) serve as terminal electron acceptors have greatly extended the natural habitats in which such organisms may predominate. Anaerobic bacteria are, however, often found in nature as members of close microbial communities (consortia) that, although sustained by syntrophic and other relations between component species, are liable to alter their composition and character in response to environmental changes, e.g., availability of terminal oxidants. It follows that the biotechnological exploitation of obligately anaerobic bacteria must be informed by knowledge both of their biochemical capacities and of their normal environmental roles. It is against this background that illustrative examples of the activities of anaerobic bacteria are considered under three heads: 1. Biodegradation/Bioremediation, with special reference to the anaerobic breakdown of aromatic and/or halogenated organic substances; 2. Biosynthesis/Bioproduction, encompassing normal and modified fermentations; and 3. Biotransformations, accomplished by whole or semipermeabilized organisms or by enzymes derived therefrom, with particular interest attaching to the production of chiral compounds by a number of procedures, including electromicrobial reduction.
Topics: Bacteria, Anaerobic; Biodegradation, Environmental; Biotechnology; Biotransformation; Fermentation; Halogens
PubMed: 7944353
DOI: 10.1007/BF02796164 -
Journal of Biotechnology Apr 2011In hypersaline environments bacteria are exposed to a high osmotic pressure caused by the surrounding high salt concentrations. Halophilic microorganisms have specific... (Review)
Review
In hypersaline environments bacteria are exposed to a high osmotic pressure caused by the surrounding high salt concentrations. Halophilic microorganisms have specific strategies for balancing the osmotic pressure and surviving in these extreme conditions. Halophilic fermentative bacteria form taxonomically and phylogenetically a coherent group mainly belonging to the order Halanaerobiales. In this review, halophilic anaerobic fermentative bacteria in terms of taxonomy and phylogeny, special characteristics, survival strategies, and potential for biotechnological applications in a wide variety of branches, such as production of hydrogen, are discussed.
Topics: Adaptation, Biological; Bacteria, Anaerobic; Biotechnology; Fermentation; Metabolic Networks and Pathways; Osmotic Pressure; Phylogeny; Salinity
PubMed: 20804793
DOI: 10.1016/j.jbiotec.2010.08.014 -
Journal of Molecular Microbiology and... 2016Acetone and other ketones are activated for subsequent degradation through carboxylation by many nitrate-reducing, phototrophic, and obligately aerobic bacteria. Acetone... (Review)
Review
Acetone and other ketones are activated for subsequent degradation through carboxylation by many nitrate-reducing, phototrophic, and obligately aerobic bacteria. Acetone carboxylation leads to acetoacetate, which is subsequently activated to a thioester and degraded via thiolysis. Two different types of acetone carboxylases have been described, which require either 2 or 4 ATP equivalents as an energy supply for the carboxylation reaction. Both enzymes appear to combine acetone enolphosphate with carbonic phosphate to form acetoacetate. A similar but more complex enzyme is known to carboxylate the aromatic ketone acetophenone, a metabolic intermediate in anaerobic ethylbenzene metabolism in denitrifying bacteria, with simultaneous hydrolysis of 2 ATP to 2 ADP. Obligately anaerobic sulfate-reducing bacteria activate acetone to a four-carbon compound as well, but via a different process than bicarbonate- or CO2-dependent carboxylation. The present evidence indicates that either carbon monoxide or a formyl residue is used as a cosubstrate, and that the overall ATP expenditure of this pathway is substantially lower than in the known acetone carboxylase reactions.
Topics: Acetone; Anaerobiosis; Bacteria, Anaerobic; Carboxy-Lyases; Ketones; Metabolic Networks and Pathways
PubMed: 26958851
DOI: 10.1159/000441500 -
International Journal of Pediatric... Jan 2005This review summarizes the information that supports the potential importance of anaerobic bacteria in tonsillitis. Some anaerobic bacteria possess interfering... (Review)
Review
This review summarizes the information that supports the potential importance of anaerobic bacteria in tonsillitis. Some anaerobic bacteria possess interfering capability with Group A beta-hemolytic streptococci (GABHS) and other pathogens. The possible role of anaerobes in the acute inflammatory process in the tonsils is supported by several observations: anaerobes have been isolated from the cores of tonsils of patients with recurrent GABHS and non-GABHS tonsillitis (NST); the recovery of anaerobes as predominant pathogens in abscesses of tonsils, in many cases without any aerobic bacteria; their recovery as pathogens in well-established anaerobic infections of the tonsils (Vincent's angina); the increased recovery rate of encapsulated pigmented Prevotella and Porphyromonas spp. in acutely inflamed tonsils; their isolation from the cores of recurrently inflamed NST; and the response to antibiotics in patients with NST. Furthermore, immune response against Prevotella intermedia is present in patients with recurrent NST, and an immune response can also be detected against P. intermedia and Fusobacterium nucleatum in patients who recovered from peritonsillar cellulitis or abscesses, infectious mononucleosis and acute non-streptococcal and GABHS tonsillitis. Although more studies are needed, these findings support the possible pathogenicity of Gram-negative anaerobic bacilli in tonsillitis.
Topics: Antibodies, Bacterial; Bacteria, Anaerobic; Humans; Palatine Tonsil; Peritonsillar Abscess; Streptococcus pyogenes; Tonsillitis; beta-Lactamases
PubMed: 15627441
DOI: 10.1016/j.ijporl.2004.08.007 -
The New Microbiologica Jul 2010Depletion of the periciliary liquid in "Cystic Fibrosis" airway disease results in reduced mucociliary transport, persistent mucus hypersecretion and consequently... (Review)
Review
Depletion of the periciliary liquid in "Cystic Fibrosis" airway disease results in reduced mucociliary transport, persistent mucus hypersecretion and consequently increased height of the luminal mucus layer, so hypoxic gradients in the mucus plugs are developed. Because of anaerobic lung zones, it is highly probable that anaerobic bacteria not detected by routine bacteriologic culture methods also reside within the mucus. Notwithstanding this evidence, microbiology laboratories working in the cystic fibrosis field do not generally use strict anaerobic bacteriologic cultures to determine the presence of anaerobic bacteria in the Cystic Fibrosis lung. The aim of this review is to focus on the published data regarding the finding of anaerobic bacteria in cystic fibrosis airway disease. Therefore, microbiology, diagnosis, antimicrobial susceptibility and possible impact on clinical management of anaerobic bacteria lung infection in cystic fibrosis are described.
Topics: Animals; Bacteria, Anaerobic; Cystic Fibrosis; Humans; Lung
PubMed: 20954436
DOI: No ID Found -
International Journal of Antimicrobial... Apr 2009This review describes the microbiology, diagnosis and management of pericarditis due to anaerobic bacteria. The predominant anaerobes isolated from patients with... (Review)
Review
This review describes the microbiology, diagnosis and management of pericarditis due to anaerobic bacteria. The predominant anaerobes isolated from patients with pericarditis are Gram-negative bacilli (mostly Bacteroides fragilis group) as well as Peptostreptococcus, Clostridium, Fusobacterium, Bifidobacterium and Actinomyces spp. Anaerobic bacteria can be recovered from pericarditis resulting from the following mechanisms: (i) spread from a contiguous site of infection, either de novo or following surgery or trauma (pleuropulmonary, oesophageal fistula or perforation, and odontogenic); (ii) spread from a site of infection within the heart, most commonly from endocarditis; (iii) haematogenous infection; and (iv) direct inoculation resulting from a penetrating injury or cardiothoracic surgery. Anaerobic Gram-negative bacilli have increased their resistance to penicillins and other antimicrobial agents in the last two decades. Identification of pathogens and determination of their antimicrobial susceptibility and beta-lactamase production are essential for adequate selection of antibiotic therapy effective against these organisms.
Topics: Anti-Bacterial Agents; Bacteria, Anaerobic; Bacterial Infections; Case Management; Humans; Microbial Sensitivity Tests; Pericarditis
PubMed: 18789852
DOI: 10.1016/j.ijantimicag.2008.06.033 -
Applied and Environmental Microbiology Apr 2021The isolation of bacteria that represent the diversity of autochthonous taxa in the gastrointestinal tract is necessary to fully ascertain their function, but the...
The isolation of bacteria that represent the diversity of autochthonous taxa in the gastrointestinal tract is necessary to fully ascertain their function, but the majority of bacterial species inhabiting the intestines of mammals are fastidious and thus challenging to isolate. The goal of the current study was to isolate a diverse assemblage of anaerobic bacteria from the intestine of pigs as a model animal and to comparatively examine various novel and traditional isolation strategies. Methods used included long-term enrichments, direct plating, a modified ichip method, as well as ethanol and tyndallization treatments of samples to select for endospore-forming taxa. A total of 234 taxa (91 previously uncultured) comprising 80 genera and 7 phyla were isolated from mucosal and luminal samples from the ileum, cecum, ascending colon, and spiral colon removed from animals under anesthesia. The diversity of bacteria isolated from the large intestine was less than that detected by next-generation sequence analysis. Long-term enrichments yielded the greatest diversity of recovered bacteria (Shannon's index [SI] = 4.7). Methods designed to isolate endospore-forming bacteria produced the lowest diversity (SI ≤ 2.7), with tyndallization yielding lower diversity than the ethanol method. However, the isolation frequency of previously uncultured bacteria was highest for ethanol-treated samples (41.9%) and the ichip method (32.5%). The goal of recovering a diverse collection of enteric bacteria was achieved. Importantly, the study findings demonstrate that it is necessary to use a combination of methods in concert to isolate bacteria that are representative of the diversity within the intestines of mammals. This work determined that using a combination of anaerobic isolation methods is necessary to increase the diversity of bacteria recovered from the intestines of monogastric mammals. Direct plating methods have traditionally been used to isolate enteric bacteria, and recent methods (e.g., diffusion methods [i.e., ichip] or differential isolation of endospore-forming bacteria) have been suggested to be superior at increasing diversity, including the recovery of previously uncultured taxa. We showed that long-term enrichment of samples using a variety of media isolated the most diverse and novel bacteria. Application of the ichip method delivered a diversity of bacteria similar to those of enrichment and direct plating methods. Methods that selected for endospore-forming bacteria generated collections that differed in composition from those of other methods with reduced diversity. However, the ethanol treatment frequently isolated novel bacteria. By using a combination of methods in concert, a diverse collection of enteric bacteria was generated for ancillary experimentation.
Topics: Animals; Bacteria, Anaerobic; Bacteriological Techniques; Endospore-Forming Bacteria; Gastrointestinal Microbiome; High-Throughput Nucleotide Sequencing; Intestines; Male; Swine
PubMed: 33608289
DOI: 10.1128/AEM.00088-21 -
Anaerobe Feb 2006The normal oropharyngeal flora contained aerobic and anaerobic bacteria that can cause respiratory infections including sinusitis. Some of these bacteria can interfere... (Review)
Review
The normal oropharyngeal flora contained aerobic and anaerobic bacteria that can cause respiratory infections including sinusitis. Some of these bacteria can interfere with the growth of potential pathogens and may play a role in preventing infections. Anaerobic bacteria emerge as pathogens as the infection becomes chronic. This may be the result of the selective pressure of antimicrobial agents that enable resistant anaerobic organisms to survive, and from the development over time of conditions appropriate for anaerobic growth, which include the reduction in oxygen tension and an increase in acidity within the sinus cavity. Anaerobes were isolated in acute maxillary sinusitis of odontogenic origin and in over half of the patients with chronic sinusitis whenever proper techniques for their cultivation were employed. These organisms were also recovered in acute sinusitis that was associated with dental infections. The predominant isolates were pigmented Prevotella and Porphyromonas, Fusobacterium and Peptostreptococcus spp.
Topics: Acute Disease; Adult; Bacteria, Aerobic; Bacteria, Anaerobic; Bacterial Infections; Child; Chronic Disease; Cross Infection; Ecosystem; Humans; Oropharynx; Population Dynamics; Sinusitis
PubMed: 16701606
DOI: 10.1016/j.anaerobe.2005.08.002