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      How Many Human and Bacteria Cells Are in the Human Body?


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          Variations of bacterial populations in human feces measured by fluorescent in situ hybridization with group-specific 16S rRNA-targeted oligonucleotide probes.

          Six 16S rRNA-targeted oligonucleotide probes were designed, validated, and used to quantify predominant groups of anaerobic bacteria in human fecal samples. A set of two probes was specific for species of the Bacteroides fragilis group and the species Bacteroides distasonis. Two others were designed to detect species of the Clostridium histolyticum and the Clostridium lituseburense groups. Another probe was designed for the genera Streptococcus and Lactococcus, and the final probe was designed for the species of the Clostridium coccoides-Eubacterium rectale group. The temperature of dissociation of each of the probes was determined. The specificities of the probes for a collection of target and reference organisms were tested by dot blot hybridization and fluorescent in situ hybridization (FISH). The new probes were used in initial FISH experiments to enumerate human fecal bacteria. The combination of the two Bacteroides-specific probes detected a mean of 5.4 x 10(10) cells per g (dry weight) of feces; the Clostridium coccoides-Eubacterium rectale group-specific probe detected a mean of 7.2 x 10(10) cells per g (dry weight) of feces. The Clostridium histolyticum, Clostridium lituseburense, and Streptococcus-Lactococcus group-specific probes detected only numbers of cells ranging from 1 x 10(7) to 7 x 10(8) per g (dry weight) of feces. Three of the newly designed probes and three additional probes were used in further FISH experiments to study the fecal flora composition of nine volunteers over a period of 8 months. The combination of probes was able to detect at least two-thirds of the fecal flora. The normal biological variations within the fecal populations of the volunteers were determined and indicated that these variations should be considered when evaluating the effects of agents modulating the flora.
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            Introduction to intestinal microecology.

            T D Luckey (1972)
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              Bacterial dry matter content and biomass estimations.

              Approximately 20% dry-matter content appears to be an accepted standard value for bacterial cells. We have found that the dry-matter content of bacteria may be more than twice as high as generally assumed. The main reason for the low estimates seems to be that proper corrections for intercellular water have not been made when estimating the wet weight of the cells. Using three different bacterial strains, we determined a dry-matter content of cells ranging from 31 to 57%, suggesting not only that the accepted standard value is much too low but also that it is far from standard. To convert bacterial biovolume into biomass (carbon content), we suggest that 0.22 g of C cm-3 should be used as a conversion factor.

                Author and article information

                Infectious Diseases and Translational Medicine
                Infect. Dis. Transl. Med.
                Infect. Dis. Transl. Med.
                International Biological and Medical Journals Publishing House Co., Limited (Room E16, 3/f, Yongda Commercial Building, No.97, Bonham Stand (Sheung Wan), HongKong )
                14 March 2017
                14 March 2017
                : 3
                : 1
                : 1-2
                From State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, No. 20, Dongdajie, Fengtai, Beijing 100071, China
                From State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, No. 20, Dongdajie, Fengtai, Beijing 100071, China
                Author notes
                Correspondence to: Yujing Bi, Email: byj7801@ 123456sina.com .

                This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

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                Figures: 0, Tables: 0, References: 10, Pages: 2
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