Detection of streptococcal mutants presumed to be defective in sugar catabolism

The presence or absence of the phosphoenolpyruvate : carbohydrate phosphotransferase system (PTS) in obligately heterofermentative group III lactobacilli including Lactobacillus brevis (3 strains), L. buchneri (2 strains) and L. fermentum (3 strains) was surveyed systematically for a series of sugars utilizable by these organisms. Contrary to common expectation, PTSs were found in two strains of L. fermentum: sucrose-PTS in one strain; sucrose-and mannose-PTSs in the other. All these activities were found to be constitutive.The phosphoenolpyruvate (PEP) : carbohydrate phosphotransferase system (PTS) is a unique sugar transport system found in bacteria. This system catalyzes the transport and concomitant phosphorylation of a number of sugars. A PTS generally consists of four proteins : enzyme I and HPr (heat-stable protein) common to all PTSs, and enzymes II and III specific for a sugar. The distribution of PTS is not ubiquitous, and when it exists, the range of sugars transported by PTS varies greatly with the bacterial species (11).Romano et al (13) studied the distribution of PTS among lactic acid bacteria by examining PTS activity for 2-deoxy-D-glucose (2DG), a non-metabolizable analogue of glucose (Glc) or mannose (Man). The PTS was present in the homofermenters such as streptococci, pediococci, and group II lactobacilli including Lactobacillus casei and L. plantarum that metabolize Glc via the Embden-MeyerhofParnas (EMP) pathway, but was absent in the heterofermenters such as leuconostocs, group III lactobacilli including L. brevis and L. buchneri, and bifidobacteria that metabolize Glc via non-EMP pathways. Since then, it is believed that PTS is linked to the EMP mode of glycolysis, that is, when a sugar is transported by a PTS, the sugar is metabolized via the EMP pathway (11). Recently, Reizer et al (12) found that certain L. brevis and L. buchneri strains had a protein similar to HPr, but no enzyme I, and concluded that a complete PTS could not operate in these organisms.We report here on a more comprehensive survey of PTSs in strains of group III lactobacilli including L. brevis, L. buchneri and L. fermentum. Unexpectedly, functional

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Inhibition of Streptococcus mutans by the antibiotic streptozotocin: mechanisms of uptake and the selection of carbohydrate-negative mutants

Jacobson

Poy

Lengeler

1990

Infect Immun

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The antibiotic streptozotocin [2-deoxy-2-(3-methyl-3-nitrosoureido)-D-glucopyranoside], an analog of Nacetylglucosamine (NAG), has been shown to be useful for the selection of carbohydrate-negative and auxotrophic bacterial mutants. We have adapted this method for use with the oral pathogen Streptococcus mutans, a gram-positive, aerotolerant anaerobe that uses predominantly carbohydrates as carbon sources for growth. Streptozotocin selectively kills growing cells of S. mutans GS-5, and under appropriate conditions it can reduce the number of viable cells in actively growing cultures by a factor of 103 to 104. However, unlike in enteric bacteria, which take up this antibiotic by a single NAG-specific transport system, streptozotocin appears to be taken up in S. mutans by both a NAG-specific system and a relatively nonspecific system that is also involved in glucose, fructose, and mannose uptake. Combining streptozotocin selection and a screening procedure involving indicator plates containing triphenyl-tetrazolium chloride, we developed a general method for the isolation of carbohydrate-negative and auxotrophic mutants of S. mutans. A preliminary characterization of both pleiotropic and specific carbohydrate-negative mutants isolated by using this procedure is presented.

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Detection of streptococcal mutants presumed to be defective in sugar catabolism

Cited by 3 publications

References 15 publications

Growth and population structure in the infaunal bivalve Yoldia eightsi in relation to iceberg activity at Signy Island, Antarctica

Growth and population structure in the infaunal bivalve Yoldia eightsi in relation to iceberg activity at Signy Island, Antarctica

Existence of Phosphoenolpyruvate: Carbohydrate Phosphotransferase Systems in Lactobacillus fermentum, an Obligate Heterofermenter

Inhibition of Streptococcus mutans by the antibiotic streptozotocin: mechanisms of uptake and the selection of carbohydrate-negative mutants

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