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Altered Schaedler flora
The altered Schaedler flora (ASF) is a community of eight bacterial species: two Lactobacilli, one Bacteroides, one spiral bacteria of the Flexistipes genus, and four extremely oxygen sensitive (EOS) Fusobacterium species.〔(J., Anderson, L., Loew, F. and Quimby F. Laboratory animal medicine. 2nd Ed. 2002. Academic Press. 46-47. )〕〔(J., Barthold, S., Davisson, M., Newcomer, C., Quimby F. and Smith, A. The mouse in biomedical research. 2nd Ed. 2007. Elsevier, Inc. 227-229. )〕〔(F., Chien, C.-C., Paster, B., Ericson, R., Orcutt, R., Schauer, D., and Fox, J. Phylogeny of the defined murine microbiota: altered Schaedler flora. 1999. ''Appl. Environ, Microbiol.'' 65(8):3287. )〕 The bacteria are selected for their dominance and persistence in the normal microflora of mice, and for their ability to be isolated and grown in laboratory settings. Germ-free animals, mainly mice, are infected with ASF for the purpose of studying the gastrointestinal (GI) tract. Intestinal commensal bacteria play an important role in affecting gene expression of the GI tract, immune responses, nutrient absorption, and pathogen resistance.〔(F., Malagelada, J. R. Review: gut flora in health and disease. 2003. ''The Lancet.'' 361(9356):512-219. )〕 The standardized microbial cocktail enabled the controlled study of microbe and host interactions, role of microbes, pathogen effects, and intestinal immunity and disease association, such as cancer, inflammatory bowel disease, diabetes, and other inflammatory or autoimmune diseases. Also, compared to germfree animals, ASF mice have fully developed immune system, resistance to opportunistic pathogens, and normal GI function and health, and are a great representation of normal mice 〔〔〔(J., Anderson, L., Loew, F. and Quimby F. Laboratory animal medicine. 2nd Ed. 2002. ''Academic Press.'' 46-47. )〕
== History ==
The GI tract is particularly difficult to study due to its complex host-pathogen interaction. With 107-1012 bacteria, 400-plus species, and variations between individuals, there are many complications in the study of a normal gastrointestinal system.〔〔 For example, it is problematic to assign biological function to specific microbes and community structure, and to investigate the respective immune responses. Furthermore, the varying mice microbiome need to be under controlled conditions for repetitions of the experiments. Germfree mice and specific pathogen free (SPF) mice are helpful in addressing some of the issues, but inadequate in many areas. Germfree mice are not a good representation of normal mice, with issues of enlarged cecum, low [eproductive rates, poorly developed immune system, and reduced health. SPF mice still contain varying microbiota, just without certain known pathogen species.〔〔〔 There is a need in the scientific field for a known bacterial mixture that is necessary and sufficient for healthy mice.
In the mid-1960s, Russell W. Schaedler isolated and grew bacteria from normal and SPF mice.〔 Aerobic and less oxygen sensitive anaerobic bacteria are easy to culture. Fusiform and EOS bacteria are difficult to culture, even though they represent the majority of the normal rodent microbiota. He selected for the bacteria that dominated and can be isolated in culture, and then colonized germfree mice with different bacteria combinations. For example, one combination could include ''Escherichia coli, Streptococcus fecalis, Lactobacillus acidophilus, L. salivarius, Bacteroides distasonis, Clostridium spp.'', and some anaerobic fusiform bacteria.〔 Certain defined microflora are able to restore germfree mice to resemble normal mice with reduced cecal volume, restored reproductive ability, colonization resistance, and well developed immune system. So named Schaedler flora, the defined microflora combinations was widely used in gnotobiotic studies.〔〔
In 1978, the National Cancer Institute revised and standardized the Schaedler flora, with the help of Roger Orcutt.〔 In what was named altered Schaedler flora, four bacteria of the original mixture were kept: the two Lactobacilli, the Bacteroides, and the EOS fusiform bacterium. Four more bacteria from the microbiome isolates were added: a spirochete bacterium and three new EOS fusiform bacteria.〔〔〔 Due to the limited technology of the time, not much was known of the specific bacterial genus and species. These bacteria are persistent and dominant in normal and SPF mice GI tract. Confirmation of the correct microbiota presence was limited to looking at the cell Morphology (biology), biochemical traits and growth characteristics 〔
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