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home:pathogenesis:microbiota [02.13.2019]
sallieq [Notes and comments]
home:pathogenesis:microbiota [01.12.2020]
sallieq [Role of Vitamin D Receptor]
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   * **Communities of microbes associated with a disease may be less diverse than controls** – irritable bowel syndrome,​(({{pubmed>​long:​19606407}})) Crohn'​s disease,​(({{pubmed>​long:​16188921}})) type I diabetes,​(({{pubmed>​long:​20613793}}))AIDS(({{pubmed>​long:​18691828}}))  ​   * **Communities of microbes associated with a disease may be less diverse than controls** – irritable bowel syndrome,​(({{pubmed>​long:​19606407}})) Crohn'​s disease,​(({{pubmed>​long:​16188921}})) type I diabetes,​(({{pubmed>​long:​20613793}}))AIDS(({{pubmed>​long:​18691828}}))  ​
   * **Microbial variability may be relatively unrelated to food intake** – While Dumas has shown that there are significant inter-regional differences in metabolites,​(({{pubmed>​long:​16579598}})) work on the oral microbiome implies this may not be due to food consumption. In studying the oral microbiome, Nasidzie //et al.// took saliva samples from people in twelve diverse regions throughout the world including China, Germany, Poland, Congo, Philippines,​ and Louisiana.(({{pubmed>​long:​19251737}})) His team concluded that "while there is significantly more diversity in bacterial genera compared from different individuals than from the same individual, the diversity among individuals from the same location is nearly the same as the diversity among individuals from different locations."​ The relative absence of variability between people in different regions implies that those factors which are highly variable, including food intake, may play a smaller than expected role in determining what at least a person'​s oral microbiota is. The Human Microbiome Research consortium concluded in 2012 that much of the diversity in healthy subjects remains unexplained.(({{pubmed>​long:​22699609}}))   * **Microbial variability may be relatively unrelated to food intake** – While Dumas has shown that there are significant inter-regional differences in metabolites,​(({{pubmed>​long:​16579598}})) work on the oral microbiome implies this may not be due to food consumption. In studying the oral microbiome, Nasidzie //et al.// took saliva samples from people in twelve diverse regions throughout the world including China, Germany, Poland, Congo, Philippines,​ and Louisiana.(({{pubmed>​long:​19251737}})) His team concluded that "while there is significantly more diversity in bacterial genera compared from different individuals than from the same individual, the diversity among individuals from the same location is nearly the same as the diversity among individuals from different locations."​ The relative absence of variability between people in different regions implies that those factors which are highly variable, including food intake, may play a smaller than expected role in determining what at least a person'​s oral microbiota is. The Human Microbiome Research consortium concluded in 2012 that much of the diversity in healthy subjects remains unexplained.(({{pubmed>​long:​22699609}}))
-  * **Many bacteria cannot be cultured using traditional cultivation techniques** – Using PCR, Fierer'​s team found that the hands of students ​subjects contained 332,000 genetically distinct bacteria belonging to 4,742 different species. 45% of the species detected were considered rare. This marked a hundred-fold increase in the number of bacterial species detected in previous studies that had relied on purely culture-based methods (such as the Petri dish) to characterize the human hand microbiota.(({{pubmed>​long:​19004758}})) ​ These conclusions are supported by the aformentioned study of NASA clean rooms, which found that only 0.1 to 55% of viable cells found via PCR were able to grow on defined culture medium.(({{pubmed>​long:​17308177}})) +  * **Many bacteria cannot be cultured using traditional cultivation techniques** – Using PCR, Fierer'​s team found that the hands of student ​subjects contained 332,000 genetically distinct bacteria belonging to 4,742 different species. 45% of the species detected were considered rare. This marked a hundred-fold increase in the number of bacterial species detected in previous studies that had relied on purely culture-based methods (such as the Petri dish) to characterize the human hand microbiota.(({{pubmed>​long:​19004758}})) ​ These conclusions are supported by the aformentioned study of NASA clean rooms, which found that only 0.1 to 55% of viable cells found via PCR were able to grow on defined culture medium.(({{pubmed>​long:​17308177}})) 
-  * **Some microbes need very few genes to persist** – The genome of the microsporidia //​Encephalitozoon cuniculi// (a pathogens ​which infects rabbits) is widely recognized as a model for extreme reduction and compaction. At only 2.9 Mbp, the genome encodes approximately 2,000 densely packed genes and little else. However, the nuclear genome of its sister, //​Encephalitozoon intestinalis//,​ is even more reduced; at 2.3 Mbp, it represents a 20% reduction from an already severely compacted genome.(({{pubmed>​long:​20865802}}))+  * **Some microbes need very few genes to persist** – The genome of the microsporidia //​Encephalitozoon cuniculi// (a pathogen ​which infects rabbits) is widely recognized as a model for extreme reduction and compaction. At only 2.9 Mbp, the genome encodes approximately 2,000 densely packed genes and little else. However, the nuclear genome of its sister, //​Encephalitozoon intestinalis//,​ is even more reduced; at 2.3 Mbp, it represents a 20% reduction from an already severely compacted genome.(({{pubmed>​long:​20865802}}))
   * **A number of bacteria never thought to exist in man, do, and in large numbers.** – A 2007 study, for example, found [[http://​www.divediscover.whoi.edu/​hottopics/​bacteria.html|hydrothermal vent eubacteria]] on a prosthetic hip joint, which represents fully 6% of the bacteria sequenced and analyzed.(({{pubmed>​long:​17501992}})) Hydrothermal vent eubacteria otherwise grow best above 176°F (80°C).   * **A number of bacteria never thought to exist in man, do, and in large numbers.** – A 2007 study, for example, found [[http://​www.divediscover.whoi.edu/​hottopics/​bacteria.html|hydrothermal vent eubacteria]] on a prosthetic hip joint, which represents fully 6% of the bacteria sequenced and analyzed.(({{pubmed>​long:​17501992}})) Hydrothermal vent eubacteria otherwise grow best above 176°F (80°C).
   * **At least in fruit flies, gut microbes can alter mating preferences** – In a [[http://​blogs.discovermagazine.com/​notrocketscience/​2010/​11/​01/​gut-bacteria-change-the-sexual-preferences-of-fruit-flies/​|2010 study]], mating preference was achieved by dividing a population of //​Drosophila melanogaster//​ and rearing one part on a molasses medium and the other on a starch medium. When the isolated populations were mixed, "​molasses flies" preferred to mate with other molasses flies and "​starch flies" preferred to mate with other starch flies. The mating preference appeared after only one generation and was maintained for at least 37 generations. Antibiotic treatment abolished mating preference, suggesting that the fly microbiota was responsible for the phenomenon.(({{pubmed>​long:​21041648}})) ​   * **At least in fruit flies, gut microbes can alter mating preferences** – In a [[http://​blogs.discovermagazine.com/​notrocketscience/​2010/​11/​01/​gut-bacteria-change-the-sexual-preferences-of-fruit-flies/​|2010 study]], mating preference was achieved by dividing a population of //​Drosophila melanogaster//​ and rearing one part on a molasses medium and the other on a starch medium. When the isolated populations were mixed, "​molasses flies" preferred to mate with other molasses flies and "​starch flies" preferred to mate with other starch flies. The mating preference appeared after only one generation and was maintained for at least 37 generations. Antibiotic treatment abolished mating preference, suggesting that the fly microbiota was responsible for the phenomenon.(({{pubmed>​long:​21041648}})) ​
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 <​mainarticle> ​ [[home:​pathogenesis:​vitamind:​metabolism|Metabolism of vitamin D and the Vitamin D Receptor]]</​article>​ <​mainarticle> ​ [[home:​pathogenesis:​vitamind:​metabolism|Metabolism of vitamin D and the Vitamin D Receptor]]</​article>​
  
-At least some of the bacteria which cause disease are intracellular. These microbes take hold progressively through a process called successive infection. Chronic forms of bacteria are able to survive and reproduce by generating substances which block and turn off the Vitamin D Receptor, a key nuclear receptor which controls the innate immune response. So logical and powerful is this survival mechanism that it seems very likely that this is the primary mode by which chronic pathogenic forms persist. It simply makes too much evolutionary sense for pathogens ​not to take full advantage of a receptor, which according to one recent study, transcribes hundreds of genes.(({{pubmed>​long:​20736230}}))+At least some of the bacteria which cause disease are intracellular. These microbes take hold progressively through a process called successive infection. Chronic forms of bacteria are able to survive and reproduce by generating substances which block and turn off the Vitamin D Receptor, a key nuclear receptor which controls the innate immune response. So logical and powerful is this survival mechanism that it seems very likely that this is the primary mode by which chronic pathogenic forms persist. It simply makes evolutionary sense for pathogens to take full advantage of a receptor, which according to one recent study, transcribes hundreds of genes.(({{pubmed>​long:​20736230}}))
  
  
home/pathogenesis/microbiota.txt · Last modified: 01.12.2020 by sallieq
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