Accumulation of acyclic polyols and trehalose as related to growth form and carbohydrate source in the dimorphic fungi Mucor rouxii and Candida albicans.

Yeast (Y) and hyphal (H) cells of Mucor rouxii and Candida albicans were cultivated in liquid media containing different carbon nutrient sources (glucose, fructose, ribose) and their free acyclic polyol and trehalose contents determined using capillary gas liquid chromatography (TMS- and OAc-derivatization). Irrespective of growth form and C-source, the fraction of the water-soluble neutral components of the cellular mass of the cultures - highly homogeneous with regard to the respective cell form produced - contained glycerol, ribitol and arabitol, in addition to trehalose. The polyols contributed 0.5-2% to the biomass of M. rouxii and 1.5-6% to that of C. albicans; the values for trehalose ranged from 0.2-11% in the former and 1-3.5% in the latter species. Mucor contained higher amounts of ribitol and arabitol in H cells and larger quantities of trehalose and glycerol in Y cells. In Candida, too, hyphae always exhibited higher ribitol contents, whereas arabitol attained higher levels in yeasts under almost any conditions - regardless of the type of medium (synthetic vs. complex), stage of culture (early vs. late log-phase) and strain used. Glycerol concentration was not correlated with the growth form; trehalose contents tended to be higher in Y cells. Taking into account the facts that C. albicans and certain Mucor species are agents of opportunistic infections and are invasive mainly in the filamentous form, and that the prospective hosts do not accumulate either of these carbohydrates, the possibility is considered of using trehalose- and polyol-metabolizing enzymes as targets for designing antifungal drugs.

Synthesis of teichoic acid by Bacillus subtilis protoplasts.

Protoplasts of Bacillus subtilis W23 readily synthesized ribitol teichoic acid from nucleotide precursors in the surrounding medium. With cytidine diphosphate-ribitol they made poly(ribitol phosphate), presumably attached to lipoteichoic acid carrier; when cytidine diphosphate-glycerol and uridine diphosphate-N-acetylglucosamine were also present a 10-fold increase in the rate of polymer synthesis occurred, and the product contained both the main chain and the linkage unit. Synthesis was inhibited by trypsin or p-chloromercuribenzenesulfonate in the medium, and we concluded that it occurred at the outer surface of the membrane. During synthesis, which was also achieved readily by whole cells after a brief period of wall lysis, the cytidine phosphate portion of the nucleotide precursors did not pass through the membrane. No evidence could be obtained for a transphosphorylation mechanism for the translocation process. It is suggested that reaction with exogenous substrates was due to temporary exposure of a protein component of the enzyme complex at the outer surface of the membrane during the normal biosynthetic cycle.

Structure of an experimentally evolved gene duplication encoding ribitol dehydrogenase in a mutant of Klebsiella aerogenes.

We have previously described a system of experimental evolution in which many of the mutants of Klebsiella aerogenes selected for faster growth on xylitol ('evolvants') synthesized elevated levels of ribitol dehydrogenase and have presented genetic evidence implicating gene duplication in the enzyme superproduction in some of the evolvants. Here we describe a physical approach to the screening for gene duplications and subsequent structure determination. Nick-translated, cloned ribitol operon (rbt) DNA was used as a hybridization probe to identify fragments containing rbt operon sequences in restriction digests of total bacterial DNA. Whilst several of the evolvants probably harbour duplications spanning the entire rbt operon, one of the spontaneously arising evolvants (strain A3) was shown to harbour a small (5.8 kilobase pairs) direct DNA repeat which encodes the dehydrogenase (but not the kinase) of the closely linked D-arabitol operon as well as the dehydrogenase (but not the kinase) of the rbt operon. The hybridization data suggest that there are 4 to 5 copies of the repeat arranged contiguously on the chromosome. The genetic instability of strain A3, the rbt fragment hybridization pattern of an A3 segregant and the activities of the pentitol catabolic enzymes in A3 are all consistent with the proposed gene duplication structure.

A switch from translational control to transcriptional control of protein synthesis in mid-exponential growth phase of bacterial cultures. Specific radioimmune labelling of ribitol-dehydrogenase-synthesising polysomes from Klebsiella aerogenes in the presence of heparin.

1. We present evidence suggesting a sudden switch from translational control to transcriptional control of protein synthesis in mid-exponential growth of bacterial batch cultures. At a critical cell density a switch from large to small polysomes occurs during a short period of exponential growth. The profile of specific polysomes engaged in synthesis of a constitutive enzyme, ribitol dehydrogenase, changes at the same point but in an opposite way: a linear profile peaking at monosomes changes to a dome-shaped profile peaking at about 15 ribosomes/mRNA, which persists into late exponential phase despite a gradual reduction in the total polysome population. The switch in the pattern of protein synthesis is exhibited dramatically by changes in the specific activity or ribitol dehydrogenase in cell extracts at different stages of batch culture. In early exponential phase the specific activity of the enzyme is constant, but it begins to rise suddenly, at the same point at which the polysome profiles change, and continues to increase up to the end of exponential phase. This effect is exhibited by the strains of Klebsiella aerogenes that are inducible for (in the presence of the inducer), consitutive for, or superproducers of ribitol dehydrogenase, and it appears to be unrelated to catabolite repression. 2. The above results depend on improved techniques for production of large amounts of bacterial polysomes and the ability to label nascent peptides attached to polysomes very specifically with radioactive antibody to ribitol dehydrogenase. Our success was due to the observation that sodium heparin completely abolishes non-specific interactions of the antibody with the polysomes.