Wall teichoic acid (WTA) is essential for the growth of Bacillus subtilis 168. To clarify the function of this polymer, the WTAs of strains 168, 104 rodBl, and 113 tagFl (rodCl) grown at 32 and 42°C were characterized. At the restrictive temperature, the rodBI and tagFl (rodCl) mutants undergo a rod-to-sphere transition that is correlated with changes in the WTA content of the cell wall. The amount of WTA decreased 33% in strain 104 rodBl and 84% in strain 113 tagFl (rodCl) when they were grown at the restrictive temperature. The extent of OL-D-glucosylation (0.84) was not affected by growth at the higher temperature in these strains. The degree of D-alanylation decreased from 0.22 to 0.10 in the rodBl mutant but remained constant (0.12) in the tagFl (rodCl) mutant at both temperatures. Under these conditions, the degree of D-alanylation in the parent strain decreased from 0.27 to 0.21. The chain lengths of WTA in strains 168 and 104 rodBI grown at both temperatures were approximately 53 residues, with a range of 45 to 60. In contrast, although the chain length of WTA from the tagFl(rodCl) mutant at 32°C was similar to that of strains 168 and 104 rodBl, it was approximately eight residues at the restrictive temperature. The results suggested that the rodBl mutant is partially deficient in completed poly(glycerophosphate) chains. The precise biochemical defect in this mutant remains to be determined. The results for strain 113 tagFl(rodCl) are consistent with the temperaturesensitive defect in the CDP-glycerol:poly(glycerophosphate) glycerophosphotransferase (H. M. Pooley, F.-X.Abellan, and D. Karamata, J. Bacteriol. 174:646-649, 1992).Wall teichoic acid plays an essential role in the growth and viability of Bacillus subtilis 168. Rod mutants of this organism which have temperature-sensitive defects in the assembly of this surface polymer undergo a rod-to-sphere transition at the restrictive temperature. To clarify the function of this polymer in surface assembly, it was our goal to characterize the teichoic acid in two of these mutants, 104 rodB1 and 113 tagF1(rodC1), under restrictive and nonrestrictive growth conditions. Rod mutants were first isolated from B. subtilis 168 by Rogers et al. (50) and Boylan and Mendelson (6). Three groups of mutations, rodA, rodB, and rodC, were defined by genetic mapping (29). The tagF1(rodC1) mutation maps at about 310° (7,29,42). This map position is within the poly(GroP) biosynthesis cluster (tag genes) (25,39). The gene cluster is organized in two divergently transcribed operons, tagABC and tagDEF (38). The genes for D-glucosylation, previously designated gtaA and gtaB, are also located in this region (47). The gtaA(tagE) gene encodes the UDP-glucose: poly(GroP) glucosyl-transferase (26, 47, 59), while the gtaB gene encodes the UDP-glucose pyrophosphorylase (39, 47). The tagF(rodC) gene codes for the CDP-glycerol:poly(GroP) glycerophosphotransferase (CGPTase) (45). In contrast, the rodBl mutation maps at about 245° (29,35,48,63 15,55,69). The degree of D-glucosylation is...

Vesicles containing lipoteichoic acid (LTA) have been isolated from Lactobacillus casei ATCC 7469 grown in the presence of either benzylpeniciUin or D-cycloserine. These cell wall antibiotics enhanced the rate of LTA and lipid secretion 6.7 times, whereas chloramphenicol inhibited their release. The formation of these vesicles from peripheral and septal wall regions did not appear to be the result of bacteriolysis. The vesicle composition of LTA and lipid was similar to that of the cytoplasmic membrane whereas the protein composition was dissimilar. The size of these vesicles ranged from 20 to 40 nm and the length of LTA ranged from 5 to 50 glycerol phosphate residues. The isolation of these vesicles provides a potential in vitro acceptor system for studying the D-alanylation of lipoteichoic acid.

It has been reported that Candida albicans can form germ-tubes only in the narrow pH range of 6-8, and that by changing only the pH one can regulate germ-tube formation. We found that the pH minimum for germ-tube formation could be dramatically lowered by eliminating the glucose present in many induction solutions. Lee's medium lacking glucose, ethanol, N-acetyl-D-glucosamine, and proline induced germ-tubes at pH values as low as 3 under most conditions. The presence of as little as 1 mM-glucose in these induction solutions was sufficient to cause the cells to grow either as yeasts with multiple buds or as pseudohyphae when the pH was 3.7. However, when C. albicans was grown in any of the above induction solutions (with the exception of ethanol), containing 200 mM-glucose buffered at pH 5.8, not only were germ-tubes formed, but their rate of formation and length were also increased. Preincubation of the cells in a solution buffered at pH 3.7 and containing 200 mM-glucose, before exposure to induction solutions lacking glucose at pH 3.7 or at pH 5.8, did not inhibit germ-tube formation. Likewise, addition of glucose after 45 min exposure to an induction solution was without effect. Theophylline and dibutyryl cAMP did not counteract the action of glucose. Other sugars which suppressed germ-tube formation at low pH were fructose, galactose, mannose, xylose, gluconic acid and the nonmetabolizable sugar 3-O-methylglucose. These results indicate that pH does not directly regulate dimorphism in C. albicans, and that glucose or its metabolites may play an important role.

Candida albicans formed germ tubes when exposed to air containing 5 to 15% carbon dioxide (CO2). The CO2-mediated germ tube formation occurred optimally at 37 degrees C in a pH range of 5.5 to 6.5. No germ tubes were produced at 25 degrees C, even when the optimal concentration of CO2 (10%) was present in the environment. The requirement of CO2 for germ tube formation could be partially substituted by sodium bicarbonate but not by N2. Carbon dioxide was required to be present throughout the entire course of germ tube emergence suggesting that its role is not limited to an initial triggering of morphogenic change. We suggest that carbon dioxide may be a common effector responsible for the germ tube promoting activity of certain chemical inducers for C. albicans.

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