|
Negativicutes
The Negativicutes are a class of bacteria in the phylum Bacillota, whose members have a peculiar cell wall with a lipopolysaccharide outer membrane which stains gram-negative, unlike most other members of the Bacillota. Although several neighbouring ''Clostridia'' species (firmicute bacteria) also stain gram-negative, the proteins responsible for the unusual diderm structure of the ''Negativicutes'' may have actually been laterally acquired from Pseudomonadota (formerly Proteobacteria). Additional research is required to confirm the origin of the diderm cell envelope in the Negativicutes. Most members of this class are obligate anaerobes, and occur in habitats such as rivers, lakes, and the intestines of vertebrates. They range from spherical forms, such as ''Megasphaera'' and ''Veillonella'', to curved rods, as typified by the selenomonads. ''Selenomonas'' has a characteristic crescent shape, with flagella inserted on the concave side, while ''Sporomusa'' is similar, but nonmo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acidaminococcaceae
The Negativicutes are a class of bacteria in the phylum Bacillota, whose members have a peculiar cell wall with a lipopolysaccharide outer membrane which stains gram-negative, unlike most other members of the Bacillota. Although several neighbouring ''Clostridia'' species (firmicute bacteria) also stain gram-negative, the proteins responsible for the unusual diderm structure of the ''Negativicutes'' may have actually been laterally acquired from Pseudomonadota (formerly Proteobacteria). Additional research is required to confirm the origin of the diderm cell envelope in the Negativicutes. Most members of this class are obligate anaerobes, and occur in habitats such as rivers, lakes, and the intestines of vertebrates. They range from spherical forms, such as ''Megasphaera'' and ''Veillonella'', to curved rods, as typified by the selenomonads. ''Selenomonas'' has a characteristic crescent shape, with flagella inserted on the concave side, while ''Sporomusa'' is similar, but non ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selenomonadales
The Selenomonadales are an order of bacteria within the class Negativicutes; unlike most other members of Bacillota, they are Gram-negative. The phylogeny of this order was initially determined by 16S rRNA comparisons. More recently, molecular markers in the form of conserved signature indels (CSIs) have been found specific for all Selenomonadales species. On the basis of these markers, the Selenomonadales are inclusive of two distinct families, and are no longer the sole order within the Negativicutes. Several CSIs have also been found specific for both families, Sporomusaceae and Selenomonadceae. Samples of bacterial strains within this order have been isolated from the root canals of healthy human teeth. Phylogeny The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI) See also * List of bacterial orders * List of bacteria genera This article lists the genera of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selenomonas
Members of the genus ''Selenomonas'' (motile crescent-shaped bacteria in general) are referred to trivially as selenomonads. The genus ''Selenomonas'' constitutes a group of motile crescent-shaped bacteria and includes species living in the gastrointestinal tracts of animals, in particular the ruminants. A number of smaller forms discovered with the light microscope are now in culture but many, especially the large selenomonads are not, owing to their fastidious and incompletely known growth requirements. Gram stain The family ''Veillonellaceae'' was transferred from the order ''Eubacteriales'' to the new order ''Selenomonadales'' in the new class ''Negativicutes''. Despite most of the members of the ''Bacillota'' staining positive for the Gram stain and being trivially called "low-GC Gram-positives" (''c.f.'' Bacterial phyla), members of the ''Negativicutes'' stain Gram-negative and possess a double bilayer. This transfer now appears to have been mistaken. On further examina ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selenomonad
Members of the genus ''Selenomonas'' (motile crescent-shaped bacteria in general) are referred to trivially as selenomonads. The genus ''Selenomonas'' constitutes a group of motile crescent-shaped bacteria and includes species living in the gastrointestinal tracts of animals, in particular the ruminants. A number of smaller forms discovered with the light microscope are now in culture but many, especially the large selenomonads are not, owing to their fastidious and incompletely known growth requirements. Gram stain The family ''Veillonellaceae'' was transferred from the order ''Eubacteriales'' to the new order ''Selenomonadales'' in the new class ''Negativicutes''. Despite most of the members of the ''Bacillota'' staining positive for the Gram stain and being trivially called "low-GC Gram-positives" (''c.f.'' Bacterial phyla), members of the ''Negativicutes'' stain Gram-negative and possess a double bilayer. This transfer now appears to have been mistaken. On further examin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacillota
The Bacillota (synonym Firmicutes) are a phylum of bacteria, most of which have gram-positive cell wall structure. The renaming of phyla such as Firmicutes in 2021 remains controversial among microbiologists, many of whom continue to use the earlier names of long standing in the literature. The name "Firmicutes" was derived from the Latin words for "tough skin," referring to the thick cell wall typical of bacteria in this phylum. Scientists once classified the Firmicutes to include all gram-positive bacteria, but have recently defined them to be of a core group of related forms called the low- G+C group, in contrast to the Actinomycetota. They have round cells, called cocci (singular coccus), or rod-like forms (bacillus). A few Firmicutes, such as ''Megasphaera'', ''Pectinatus'', ''Selenomonas'' and ''Zymophilus'', have a porous pseudo-outer membrane that causes them to stain gram-negative. Many Bacillota (Firmicutes) produce endospores, which are resistant to desiccation and can ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Veillonellaceae
The Veillonellaceae are a family of the Clostridia, formerly known as Acidaminococcaceae. Bacteria in this family are grouped together mainly based on genetic studies, which place them among the Bacillota. Supporting this placement, several species are capable of forming endospores. However, they differ from most other Bacillota in having Gram-negative stains. The cell wall composition is peculiar. Members of this family are all obligate anaerobes, and occur in habitats such as rivers, lakes, and the intestines of vertebrates. They range from spherical forms, such as ''Megasphaera'' and ''Veillonella'', to curved rods, as typified by the Selenomonads. ''Selenomonas'' has a characteristic crescent-shape, with flagella inserted on the concave side, while ''Sporomusa'' is similar but non-motile. Their names refer to this distinctive morphology: ''selene'' means moon, and ''musa'' means banana. The name Selenobacteria also refers to some this group. The description of this ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acidaminococcus
''Acidaminococcus'' is a genus in the phylum Bacillota (Bacteria), whose members are anaerobic diplococci that can use amino acids as the sole energy source for growth. Like other members of the class Negativicutes, they are gram-negative, despite being Bacillota, which are normally gram-positive. Etymology The name ''Acidaminococcus'' derives from:New Latin noun ''acidum'' (from Latin adjective ''acidus'', sour), an acid; New Latin adjective ''aminus'', amino; New Latin masculine gender noun ''coccus'' (from Greek masculine gender noun ''kokkos (κόκκος)'', grain, seed), coccus-shaped; New Latin masculine gender noun ''Acidaminococcus'', the amino acid coccus. Phylogeny The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI) See also * Bacterial taxonomy * Microbiology * ''Selenomonas'' * List of bacterial orders * List of bacteria genera This article list ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gram-negative Bacteria
Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall sandwiched between an inner cytoplasmic cell membrane and a bacterial outer membrane. Gram-negative bacteria are found in virtually all environments on Earth that support life. The gram-negative bacteria include the model organism ''Escherichia coli'', as well as many pathogenic bacteria, such as ''Pseudomonas aeruginosa'', '' Chlamydia trachomatis'', and ''Yersinia pestis''. They are a significant medical challenge as their outer membrane protects them from many antibiotics (including penicillin), detergents that would normally damage the inner cell membrane, and lysozyme, an antimicrobial enzyme produced by animals that forms part of the innate immune system. Additionally, the outer leaflet of this membrane comprises a complex lipopol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clostridia
The Clostridia are a highly polyphyletic class of Bacillota, including '' Clostridium'' and other similar genera. They are distinguished from the Bacilli by lacking aerobic respiration. They are obligate anaerobes and oxygen is toxic to them. Species of the class ''Clostridia'' are often but not always Gram-positive (see ''Halanaerobium'') and have the ability to form spores. Studies show they are not a monophyletic group, and their relationships are not entirely certain. Currently, most are placed in a single order called Clostridiales, but this is not a natural group and is likely to be redefined in the future. Most species of the genus ''Clostridium'' are saprophytic organisms that ferment plant polysaccharides and are found in many places in the environment, most notably the soil. However, the genus does contain some human pathogens (outlined below). The toxins produced by certain members of the genus ''Clostridium'' are among the most dangerous known. Examples are tetanus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Veillonella
''Veillonella'' are Gram-negative bacteria (Gram stain pink) anaerobic cocci, unlike most Bacillota, which are Gram-positive bacteria. This bacterium is well known for its lactate fermenting abilities. It is a normal bacterium in the intestines and oral mucosa of mammals. In humans they have been implicated in cases of osteomyelitis and endocarditis, for example with the species ''Veillonella parvula''. ''Veillonella dispar'' is the most nitrate-reducing bacterium in the oral cavity, which is beneficially anti-bacterial. When ''Veillonella'' is responsible for clinical infections in humans, it should be kept in mind that more than 70% of the strains are resistant to penicillin. Fermentation Lactate is fermented to propionate and acetate by the methylmalonyl-CoA pathway. Little ATP is produced in this fermentation. High substrate affinity is suggested to be the reason. 3 Lactate → acetate + 2 propionate + + A study of Veillonella in endurance athletes found that a rela ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genome Taxonomy Database
The Genome Taxonomy Database (GTDB) is an online database that maintains information on a proposed nomenclature of prokaryotes, following a phylogenomic approach based on a set of conserved single-copy proteins. In addition to breaking up paraphyletic groups, this method also reassigns taxonomic ranks algorithmically, creating new names in both cases. Information for archaea was added in 2020, along with a species classification based on average nucleotide identity. Each update incorporates new genomes as well as human adjustments to the taxonomy. An open-source tool called GTDB-Tk is available to classify draft genomes into the GTDB hierarchy. The GTDB system, via GTDB-Tk, has been used to catalogue not-yet-named bacteria in the human gut microbiome and other metagenomic sources. The GTDB is incorporated into the ''Bergey's Manual of Systematics of Archaea and Bacteria'' in 2019 as its phylogenomic resource. See also * PhyloCode * National Center for Biotechnology Informa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
