Roles of Lactobacillus in the Intestinal Tract

259

Roles of Lactobacillus in the Intestinal Tracf1

WILLIAM E. SANDINE

Department ofMicrobiology, Oregon State University. Corvallis, Oregon 97331

(Received for publication August 14, 1978)

ABSTRACT billion per gram. Their absence in certain "healthy" Despite the opinion of many scientists and laymen that lactobacilli persons would suggest that while their function may be Downloaded from http://meridian.allenpress.com/jfp/article-pdf/42/3/259/1649905/0362-028x-42_3_259.pdf by guest on 27 September 2021 benefit adult intestinal health, the medical and scientific communities desirable, it may also be dispensible. Lactobacilli are not do not accept this as fact. This paper offers possible beneficial and the most numerous bacteria in the Gl tract as illustrated detrimental roles which lactobacilli could play; relevant literature citations also are made. Healthful roles include those exerted as a result in Table 2. This would suggest that if their intestinal of their presence as members of the intestinal flora as well as their metabolic activities are beneficial to man they would be benefits as culture or enzyme preparations. Speculative detrimental useful because of what a relatively few, that is from a effects discussed are nutrient competition, carcinogen activation and hundred per gram to 500 million per gram, could do. But detoxification interference (glucuronide hydrolysis). all food microbiologists are aware that it isn't always the total number of bacteria present that is important, but In moving from the stomach through the intestinal the type. In this regard it is of interest that certain tract, food passes through the duodenum, jejunum and individuals lack or have low numbers of coliforms in ileum of the small intestine and the ascending, transverse stool samples due to antibiotic production by a and descending colon of the large intestine. For many TABLE 1. Number of lactobacilli in the human stomach, intestinal microorganisms. this is a hostile environment where a tract number of factors or compounds, contributed in part by lactobacilli, discourage growth and in some instances Sample Source Viable count (rangle log10/g) survival of undesirable bacteria. These factors include gastric juice, bile, fatty acids, organic acids, hydrogen Upper small intestine N-6 sulfide, lysozyme, lysolecithin, antibiotics and peristalsis. Lower small intestine N-8 Large intestine N-9 In this discussion we will be concerned with bacteria of Feces 3.6-9.3 the Lactobacillus genus and consider the roles these a Adopted from Drasar (6) and Drasar and Hill (8). bacteria might have in the intestinal tract. If they play bN =less than 10 per gram. any role at all, it follows that they would be present in a reasonable number in most humans. Savage (26) and non-sporeforming variant of Bacillus subtilis (18). In others have indicated that this is the case. Table 1 these situations, the population of these bacteria do not summarizes data indicating the approximate number of exceed 104 per gram of feces (Gerhardt. personal lactobacilli present in the intestinal tract. Here it may be communication) but lactobacilli are increased. seen that they range from not detectable in some individuals, except for the feces, to from a million to a FUNCTIONS OF LACTOBACILLI We might speculate about functions the lactobacilli 'Paper presented at 1978 annual meeting of American Society for Microbiology, May 14-19. Las Vegas, Nevada, Technical Paper No. could play in the human intestinal tract and some 4932. Oregon Agricultural Experiment Station. suggested roles are shown in Table 3. Three possible

Table 2. Approximate numbers

Genus

Bif!dobacterium N 2.0 4.0 7.0 10.5 Clostridium N N N N 3.0 Enterobacteria N N 3.3 7.0 6.0 Enterococci N N 2.3 7.0 3.5 Lactobacillus N 1.0 N 6.5 4.0 Veillonella N N N 3.0 3.0 Yeasts N 1.0 2.3 N 1.0 14 x w-6 260 SAN DINE detrimental roles, nutrient competition, carcinogen acids (40 o/o each) and deoxycholic acid (10 o/o) (2). They aid activation, and glucuronide hydrolysis are suggested in digestion by forming polymolecular aggregates while nine beneficial attributes are listed. Published (micelles) with water-insoluble lipids and fat-soluble research reports will support some of these roles for vitamins (19) and are recycled as conjugates of glycine lactobacilli while others are speculative. and taurine (3: 1 ratio). Deconjugated bile acids are more Since 1947 (15) a number of reports reviewed recently inhibitory for bacteria than the conjugated acids (9) and (20,27,28) have been made concerning antibiotic deconjugation is one of the main microbial reactions production by lactobacilli. These have been called by which alter the bile acids. The small intestine contains various names including acidophilin, acidolin, lacto little free bile acids but significant quantities appear in bacillin and lactocidin. Strains vary in their ability to the large bowel. They may function here to control the produce these substances and cultural conditions microbial composition but no evidence proves that this is influence the amount produced within strains. In vitro so (26). If this is important, it would be worthwhile to

inhibitory activity has been reported against salmonellae, examine lactobacilli for their ability in this regard. Downloaded from http://meridian.allenpress.com/jfp/article-pdf/42/3/259/1649905/0362-028x-42_3_259.pdf by guest on 27 September 2021 shigellae, staphylococci, Proteus. Klebsiella, pseudo Gilliland and Speck (I I) have tested human fecal monads, enteropathogenic Escherichia coli, bacilli and lactobacilli (L. acidophilus, L. buchneri, L. casei, L. Vibrio organisms. In vivo studies with human medical fermentum, L. leichmannii, L. plantarum, L. salivarius) and intestinal surgery patients are needed to determine for deconjugation of glycocholate and taurocholate. Only if these antibiotic substances benefit intestinal health. L. buchneri strains were inactive on both conjugates and Organic acids such as acetic and lactic which are all of six L. acidophilus isolates tested deconjugated produced by lactic acid bacteria will inhibit growth taurocholate (Table 4). Thus lactobacilli can liberate free of many bacteria, especially pathogenic gram-negative bile acids in the intestinal tract and thereby could exert types. A number of literature reports have dealt with an influence on the balance of bacteria present. this phenomenon (5,13,29) and have shown that while pH per se is a factor, lower pH values also potentiate the TABLE 4. Ability of lactobacilli from human feces to deconjugate bile acidsa. activity of these acids since the undissociated forms are most destructive. Also these volatile acids are especially Species Taurocholate Glycocholate antimicrobial under the low oxidation-reduction po L. acidophilus 6/6 116 tentials (26) which lactic acid bacteria help maintain in L. buchneri 0/3 0/3 9/13 the intestines. Diet may be a factor determining the L. casei 0/13 L.fermentum 115 3/5 amount of these acids produced as, for example, with L. leichmannii 3/4 314 breast-fed human infants (3,4). Here, bifidobacteria, L. plantarum 0/3 2/3 1/2 1/2 which derive growth-promoting oligosaccharides from L. salivarius human milk, produce acetate and lactate homofermen a Data of Gilliland and Speck (11). No. positive/No. strains. tatively resulting in a fecal pH of about 5.0. Apart from the growth-products influence lactobacilli COLON CANCER likely have in suppressing undesirable bacteria in the Interactive effects between food constituents and intestinal tract, they may also out-compete other bacteria bacteria in the intestine are believed involved in the for nutrients and occupy sites as gut colonizers and make etiology of colon cancer (7,1 7). Glucuronide formation in these sites unavailable to other microorganisms (10). the liver is an important detoxification mechanism in Data supporting these possibilities are not available from humans; the glucuronides formed are excreted with bile research involving humans but hopefully will be and may be hydrolyzed by certain intestinal bacteria to forthcoming. Recent studies in animals, however, release a potential carcinogen. Other enzymatic capabil support such a model (21,23). ities of the intestinal microflora may also be involved in carcinogen production such as reduction of azo and BILE SALTS aromatic nitrogen compounds through azoreductase and Bile salts are surface-active chemicals produced in the nitroreductase activities. Steroid and protein metabolites liver from the catabolism of cholesterol. The bile acids produced by bacteria have also been shown to yield produced in humans are chenodeoxycholic and cholic carcinogens or co-carcinogens (7). The role that

TABLE 3. Possible functions for lactobacilli in the intestinal tract.

Beneficial Nat ural flora Adjunct Detrimental 1. Antibiotic production 1. Disease therapy 1. Nutrient com petition 2. Organic acid production 2. Preventative therapy 2. Carcinogen activation 3. Lower pH and 0/R 3. Enzyme source 3. Glucuronide hydrolysis 4. Competitive antagonists 5. Bile deconjugation 6. Carcinogen suppression ROLES OF INTESTINAL LACTOBACILLI 261 lactobacilli play in these processes in the human intestine and clinically, that the use of "sour milk" as an article of is difficult to access. In the rat, Lactobacillus species diet checks or altogether arrests this unhealthy have been ranked third in {3-glucuronidase activity fermentation in the intestine by planting there the lactic behind the Bacteroids and bifidobacteria. However. in bacillus which, forming lactic acid, renders the life and humans, as shown in Table 5, this activity in the intestine growth of the bacteria of those special poisonous as contributed by the microflora is very low. In a recent fermentations (which cannot flourish in an acid study with rats, the influence of diet, advanced age and environment) impossible. Hence he himself daily took a dietary supplements of Lactobacillus acidophilus (1010 pint or so of sour milk, and he recommended it to others viable cells per animal per day) on the bacterial enzymes and arranged for the commercial preparation of a {3-glucuronidase, azoreductase and nitroreductase in the particularly pure and agreeable "sour milk" from the fecal microflora was measured (14). Feeding the L. sale of which he scrupulously abstained from deriving acidophilus supplement significantly lowered the latter any pecuniary profit. This small, though valuable,

two enzymes in animals on a high meat diet. Lactobacilli adventure of his in dietetics has been-unfortunately, but Downloaded from http://meridian.allenpress.com/jfp/article-pdf/42/3/259/1649905/0362-028x-42_3_259.pdf by guest on 27 September 2021 also have been shown to be active in degrading perhaps inevitably- the one and only feature of his long nitrosamines {24). career of vast scientific discovery which has impressed itself on the somewhat erratic intelligence of the ''man in TABLE 5. Bacterial (3-glucuronidase activity of the intestirwl the street." contents from man and laboratory animalsa. Since 1916 fascination with acidophilus milk as a Activityb health food has continued, especially the last few years Species Upper small Lower small when unfermented or sweet acidophil us milk has become Man .02 a retail market item in the U.S. Definition of the roles Rabbit 2.4 45.4 that L. acidophilus and other lactobacilli play in Guinea-pig 2.7 139 Rat 304 1341 intestinal health requires further research attention. But 1200 5015 clearly, the properties of these bacteria which we have

a Data ofHawksworth eta!. (16). emphasized here indicate they are beneficial members of b1-4moles of phenolphthalein glucuronide degraded per h/g. the human intestinal flora.

REFERENCES DIETARY ADJU~CTS 1. Anonymous. 1976. Interrelationships of diet, gut micro flora nutrition and health. Dairy Council Digest 47(4): 14-24. The potential beneficial activities of lactobacilli in the 2. Brandt, L. 1., and L. H. Bernstein. 1976. Bile salts: their role in human intestinal tract has led to their use or suggested cholesterol synthesis, secretion and lithogenesis. Am. J. Gastro· use as dietary adjuncts for at least three purposes: (a) in enterol. 65:17-30. intestinal disease therapy, (b) to improve or maintain 3. Bullen, C. L.. and P. V. Tearle. 1976. Bifidobacteria in the intestinal health and (c) as a source of {3-galactosidase to intestinal tract of infants: an in-vitro study. J. Med. Microbio!. 9: 335-344. enable lactose-intolerant persons to consume milk 4. Bullen, C. L, P. V. Tearle, and A. T. Willis. 1976. Bifidobacteria in (Table 3); many articles on these applications have been the intestinal tract of infants: an in-vivo study. J. Med. Microbiol. published including three recent reviews (1,25,30). While 9:325-333. consumption may not increase the numbers of viable 5. Daly, C., W. E. Sandine, and P. R. Elliker. 1972. Interaction of lactobacilli in the feces (12), the metabolic activity of the food starter cultures and food-borne pathogens: Streptococcus diacetilactis versus food pathogens. J. Milk Food Techno!. intestinal microflora may thereby be beneficially altered 35:349-357. (14), especially if the organisms are consumed regularly. 6. Drasar, B. S.1974. The normal microbial flora of man. pp. 187-196. One recent report {22), however, indicated that In: F. A. Skinner and J. G. Carr (eds.) Academic Press, London. commercially prepared tablets containing L. acidophilus 7. Drasar, B.S., and M. J. HilL 1972. Intestinal bacteria and cancer. and Lactobacillus bulgaricus were ineffective in reducing Am. J. Clin. Nutr. 25:1399-1404. 8. Drasar. B. S., and M. J. Hill. 1974. Human intestinal flora. the incidence or duration of traveler's diarrhea. Academic Press, London. pp. 1-163. On this occasion it is appropriate to read a portion of 9. Floch, M. H., H. J. Binder, B. Filburn, and W. Gershengoren. the obituary (Nature 97(2439):443, 1916) of Elias 1972. The effect of bile acids on intestinal microflora. Am. J. Clin. Metchnikoff (1845-1916) who, from his early studies in Nutr. 25:1418-1426. intestinal microbiology, suggested that Lactobacillus 10. Fuller, R. 1972. Bacteria that stick in the gut. New Scientist 30: 506-507. organisms were beneficial to human intestinal health. .II. Gilliland. S. E., and M. L. Speck. 1977. Deconjugation of bile acids "In 1903 he found time to write a profoundly interesting by intestinallactobacilli. App!. Environ. Microbio!. 33:15-18. popular book, The Nature of Alan (London:Heinemann), 12. Gilliland, S. E., M. L. Speck. G. F. Nauyok, and F. G. Giesbrecht. in which, among other things, he discourses on old age, 1978. Influence of consuming Lactobacillus acidophilus on fecal and his view that unhealthy fermentation commonly flora of healthy males. J. Dairy Sci. 61:1·10. 13. Goepfert, J, M., and R. Hicks. 1969. Effect of volatile fatty acids on occurring in the large intestine produces poisons which Salmonella typhimurium. J. Bacteriol. 97:956-958. are absorbed, and lead to deterioration of the tissues of Goldin, B., and S. L. Gorbach. 1977. Alterations in fecal the walls of the arteries, and so to senile changes and microflora enzvmes related to diet. age, Lactobacillus supplements unduly early death. He satisfied himself, experimentally and dimethylh~drazine. Cancer40:2421-2426. 262 SAN DINE

15. Grossowics, N .. D. Kaplan, and S. Schneerson. 1947. Production of diarrhea. A randomized, double blind clinical trial. Gastroenter antibiotic substances by a lactobacillus. Int. Congr. Microbiol. 5th, ology 74:829-870. p.137-138, RiodeJanerio. 23. Roach, S., D. C. Savage. and G. W. Tannock. 1977. Lactobacilli 16. Hawksworth. G., B. S. Drasar. and M. J. Hill. 1971. Intestinal isolated from the stomach of conventional mice. Appl. Environ. bacteria and the hydrolysis of glycosidic bonds. J. Med. Microbial. Microbial. 33:1197-1203. 4:451-459. 24. Rowland, I. R., and P. Grasso. 1975. Degradation of N-nitro 17.Hill, M. J., B. S. Drasar, V. Aries, J. S. Crowither, G. M. samines by intestinal bacteria. Appl. Microbial. 29:7-12. Hawksworth, and R. E. 0. Williams. 1971. Bacteria and etiology of 25. Sandine, W. E., K. S. Muralidhara, P. R. Elliker, and D. C. cancer of the large bowel. Lancet 1:95-100. England. 1972. Lactic acid bacteria in food and health: A review 18. Iglewski, W. J., and N. Gerhardt. 1978. Identification of an with special reference to enteropathogenic Escherichia coli as well antibiotic-producing bacterium from the human intestinal tract as certain enteric diseases and their treatment with antibiotics and and characterization of its antimicrobial product. Antimicrobial lactobacilli. J. Milk Food TechnoI. 35:691-702. Agents Chemother.13:81-89. 27. Shahani, K. M., J. R. Vakil, and A. Kilara. 1976. Natural anti 19. Midtvedt, T., and A. Norman. 1972. Adsorption of bile acids to biotic activity of Lactobacillus acidophilus and bulgaricus. I. intestinal microorganisms. Acta Path. Microbial. Scand. Sec. B. Cultural conditions for the production of antibiosis. Cultured Dairy

80:202-210. Products J. 1114): 14-17. Downloaded from http://meridian.allenpress.com/jfp/article-pdf/42/3/259/1649905/0362-028x-42_3_259.pdf by guest on 27 September 2021 20. Mikolajcik, E. M.. and I. Y. Hamdan. 1975. Lactobacillus 28. Shahani, K. M., J. R. Vakil, and A. Kilara. 1977. Natural acidophilus. II. Antimicrobial agents. Cultured Dairy Products J. antibiotic activity of Lactobacillus acidophilus and bulgaricus. II. 10(1): 18.20. Isolation of acidophilin from L. acidophilus. Cultured Dairy 21. Muralidhara, K. S., G. G. Sheggeby, P.R. Elliker, D. C. England Products J. 12(2):8-11. and W. E. Sandine. 1977. Effect of feeding lactobacilli on the 29. Sorrells, K. M., and M. L. Speck. 1970. Inhibition of Salmonella coliform and Lactobacillus flora of intestinal tissue and feces from ga/linarum by culture filtrates of Leuconostoc citrovorum. J. Dairy piglets. J. Food Prot. 40:288-295. Sci. 53:239-241. 22. Pozo Olano, J., J. H. Warram, Jr., R. G. Gomex, and M. G. 30. Speck, M. L. 1976. Interactions among lactobacilli and man. J. Cavazos. 1978. Effect of a lactobacilli preparation on traveler's Dairy Sci. 59:338-343.