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An anaerobic organism or anaerobe is any organism that does not require molecular oxygen for growth. It may react negatively or even die if free oxygen is present. In contrast, an aerobic organism (aerobe) is an organism that requires an oxygenated environment. Anaerobes may be unicellular or multicellular. Most fungi are obligate aerobes, requiring oxygen to survive. However, some species, such as the Chytridiomycota that reside in the rumen of cattle, are obligate anaerobes; for these species, anaerobic respiration is used because oxygen will disrupt their metabolism or kill them. The sea floor is possibly one of the largest accumulation of anaerobic organisms on Earth, where microbes are primarily concentrated around hydrothermal vents. These microbes produce energy in absence of sunlight or oxygen through a process called chemosynthesis, whereby inorganic compounds such as hydrogen gas, hydrogen sulfide or ferrous ions are converted into organic matter.
The human microbiome is the aggregate of all microbiota that reside on or within human tissues and biofluids along with the corresponding anatomical sites in which they reside, including the gastrointestinal tract, skin, mammary glands, seminal fluid, uterus, ovarian follicles, lung, saliva, oral mucosa, conjunctiva, and the biliary tract. Types of human microbiota include bacteria, archaea, fungi, protists, and viruses. Though micro-animals can also live on the human body, they are typically excluded from this definition. In the context of genomics, the term human microbiome is sometimes used to refer to the collective genomes of resident microorganisms; however, the term human metagenome has the same meaning.
Bacillota is 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 branches of science known informally as omics are various disciplines in biology whose names end in the suffix -omics, such as genomics, proteomics, metabolomics, metagenomics, phenomics and transcriptomics. Omics aims at the collective characterization and quantification of pools of biological molecules that translate into the structure, function, and dynamics of an organism or organisms.
Metagenomics is the study of genetic material recovered directly from environmental or clinical samples by a method called sequencing. The broad field may also be referred to as environmental genomics, ecogenomics, community genomics or microbiomics.
Dysbiosis is characterized by a disruption to the microbiome resulting in an imbalance in the microbiota, changes in their functional composition and metabolic activities, or a shift in their local distribution. For example, a part of the human microbiota such as the skin flora, gut flora, or vaginal flora, can become deranged (unbalanced), when normally dominating species become underrepresented and species that normally are outcompeted or contained increase to fill the void. Similar to the human gut microbiome, diverse microbes colonize the plant rhizosphere, and dysbiosis in the rhizosphere, can negatively impact plant health. Dysbiosis is most commonly reported as a condition in the gastrointestinal tract or plant rhizosphere.
The Human Microbiome Project (HMP) was a United States National Institutes of Health (NIH) research initiative to improve understanding of the microbiota involved in human health and disease. Launched in 2007, the first phase (HMP1) focused on identifying and characterizing human microbiota. The second phase, known as the Integrative Human Microbiome Project (iHMP) launched in 2014 with the aim of generating resources to characterize the microbiome and elucidating the roles of microbes in health and disease states. The program received $170 million in funding by the NIH Common Fund from 2007 to 2016.
Microbiota are the range of microorganisms that may be commensal, mutualistic, or pathogenic found in and on all multicellular organisms, including plants. Microbiota include bacteria, archaea, protists, fungi, and viruses, and have been found to be crucial for immunologic, hormonal, and metabolic homeostasis of their host.
Alistipes is a Gram-negative genus of rod-shaped anaerobic bacteria in the phylum Bacteroidota. When members of this genus colonize the human gastrointestinal (GI) tract, they provide protective effects against colitis, and cirrhosis [citations needed]. However, this genus can also cause dysbiosis by contributing to anxiety, chronic fatigue syndrome, depression, and hypertension. Showcasing priority effects in microbiome assembly, when infant GI tracts have bacteria of the species Staphylococcus but not the species Faecalibacterium, Alistipes species become less capable of colonization. Alistipes, typically benign in the gut, can sometimes trigger infections like intra-abdominal abscesses and bloodstream infections, emphasizing the fine line between symbiosis and disease. This underscores the significance of comprehending their impact on human health within microbial ecosystems.
Sutterella is a genus of Gram-negative, rod-shaped, non-spore-forming, Betaproteobacteria whose species have been isolated from the human gastrointestinal tract as well as canine feces. The genus of the family Sutterellaceae currently encompasses 4 distinct species, though at least 5 additional species have been proposed that do not yet meet International Code of Nomenclature of Prokaryotes (ICNP) standards for classification. Sutterella are frequently referred to as commensal in the context of human hosts, but are associated with inflammation, which has implications for a number of diseases.
Akkermansia muciniphila is a human intestinal symbiont, isolated from human feces. It is a mucin-degrading bacterium belonging to the genus Akkermansia, discovered in 2004 by Muriel Derrien and Willem de Vos at Wageningen University of the Netherlands. It belongs to the phylum Verrucomicrobiota and its type strain is MucT. It is under preliminary research for its potential association with metabolic disorders.
Methanobrevibacter oralis is a methanogenic archaeon species considered to be a member of the human microbiota, mainly associated to the oral cavity. M. oralis is a coccobacillary shaped, single-cell, Gram-positive, non-motile microorganism of the Archaea domain of life. This species has been isolated and sequenced from humans in dental plaque and in their gastrointestinal tract. As a methanogen and a hydrogenotroph, this prokaryote can produce methane by using hydrogen and carbon dioxide as substrates through a process called methanogenesis.
Mark J. Pallen is a research leader at the Quadram Institute and Professor of Microbial Genomics at the University of East Anglia. In recent years, he has been at the forefront of efforts to apply next-generation sequencing to problems in microbiology and ancient DNA research.
A microbiome is the community of microorganisms that can usually be found living together in any given habitat. It was defined more precisely in 1988 by Whipps et al. as "a characteristic microbial community occupying a reasonably well-defined habitat which has distinct physio-chemical properties. The term thus not only refers to the microorganisms involved but also encompasses their theatre of activity". In 2020, an international panel of experts published the outcome of their discussions on the definition of the microbiome. They proposed a definition of the microbiome based on a revival of the "compact, clear, and comprehensive description of the term" as originally provided by Whipps et al., but supplemented with two explanatory paragraphs, the first pronouncing the dynamic character of the microbiome, and the second clearly separating the term microbiota from the term microbiome.
Metatranscriptomics is the set of techniques used to study gene expression of microbes within natural environments, i.e., the metatranscriptome.
Christensenella is a genus of non-spore-forming, anaerobic, and nonmotile bacteria from the family Christensenellaceae. They are also part of the order Clostridiales, the class Clostridia and the phylum Firmicutes. Phylogenetic analyzes of 16S rRNA gene sequences are used to describe this family. Due to the recent discovery of the Christensenellaceae family, it was not given importance until a few years ago. This is why very little is known about its ecology and how it may be associated with host factors and other microbiota. However, recent studies establish that members of this family, with exceptions, may be associated with a healthy phenotype for humans. The species C. minuta has been published and validated, and C. timonensis and C. massiliensis have been proposed as novel species of the genus Christensenella, all isolated from human feces.
Pharmacomicrobiomics, proposed by Prof. Marco Candela for the ERC-2009-StG project call, and publicly coined for the first time in 2010 by Rizkallah et al., is defined as the effect of microbiome variations on drug disposition, action, and toxicity. Pharmacomicrobiomics is concerned with the interaction between xenobiotics, or foreign compounds, and the gut microbiome. It is estimated that over 100 trillion prokaryotes representing more than 1000 species reside in the gut. Within the gut, microbes help modulate developmental, immunological and nutrition host functions. The aggregate genome of microbes extends the metabolic capabilities of humans, allowing them to capture nutrients from diverse sources. Namely, through the secretion of enzymes that assist in the metabolism of chemicals foreign to the body, modification of liver and intestinal enzymes, and modulation of the expression of human metabolic genes, microbes can significantly impact the ingestion of xenobiotics.
Anaerococcus is a genus of bacteria. Its type species is Anaerococcus prevotii. These bacteria are Gram-positive and strictly anaerobic. The genus Anaerococcus was proposed in 2001. Its genome was sequenced in August 2009. The genus Anaerococcus is one of six genera classified within the group GPAC. These six genera are found in the human body as part of the commensal human microbiota.
Gabonibacter is a genus from the family of Porphyromonadaceae which have been isolated from human sources.
The human milk microbiota, also known as human milk probiotics (HMP), encompasses the microbiota–the community of microorganisms–present within the human mammary glands and breast milk. Contrary to the traditional belief that human breast milk is sterile, advancements in both microbial culture and culture-independent methods have confirmed that human milk harbors diverse communities of bacteria. These communities are distinct in composition from other microbial populations found within the human body which constitute the human microbiome.
References
- ↑ Lagier J, Armougom F, Million M, et al. (December 2012). "Microbial culturomics: paradigm shift in the human gut microbiome study". Clinical Microbiology and Infection. 18 (12): 1185–1193. doi: 10.1111/1469-0691.12023 . PMID 23033984.
- 1 2 Lagier J, Khelaifia S, Alou M, et al. (December 2016). "Culture of previously uncultured members of the human gut microbiota by culturomics". Nature Microbiology. 1 (12): 16203. doi: 10.1038/nmicrobiol.2016.203 . PMID 27819657. (Retracted, see doi:10.1038/s41564-024-01894-5, PMID 39578579 )
- 1 2 3 Greub, G. (December 2012). "Culturomics: a new approach to study the human microbiome". Clinical Microbiology and Infection. 18 (12): 1157–1159. doi: 10.1111/1469-0691.12032 . PMID 23148445.
- ↑ Rinke C, Schwientek P, Sczyrba A, et al. (25 July 2013). "Insights into the phylogeny and coding potential of microbial dark matter". Nature. 499 (7459): 431–437. Bibcode:2013Natur.499..431R. doi: 10.1038/nature12352 . hdl: 10453/27467 . PMID 23851394.
- ↑ Diakite A, Dubourg G, Dione N, et al. (December 2020). "Optimization and standardization of the culturomics technique for human microbiome exploration". Scientific Reports. 10 (1): 9674. Bibcode:2020NatSR..10.9674D. doi: 10.1038/s41598-020-66738-8 . PMC 7295790 . PMID 32541790.
- ↑ Chang Y, Hou F, Pan Z, et al. (17 December 2019). "Optimization of culturomics strategy in human fecal samples". Frontiers in Microbiology. 10: 2891. doi: 10.3389/fmicb.2019.02891 . PMC 6927924 . PMID 31921067.
- ↑ Diakite A, Dubourg G, Dione N, et al. (21 October 2019). "Extensive culturomics of 8 healthy samples enhances metagenomics efficiency". PLOS ONE. 14 (10): e0223543. Bibcode:2019PLoSO..1423543D. doi: 10.1371/journal.pone.0223543 . PMC 6802823 . PMID 31634343. (This paper currently has an expression of concern, see doi:10.1371/journal.pone.0278361, PMID 36512561, Retraction Watch )