Modulation of an apparent mRNA pool for extracellular protease in Bacillus amyloliquefaciens

Effect of temperature shifts on extracellular proteinase-specific mRNA pools in Pseudomonas fluorescens B52

The influence of a shift in temperature from 20 to 32 degrees C on extracellular proteinase synthesis by Pseudomonas fluorescens B52 was examined. When cells actively synthesizing proteinase at 20 degrees C were shifted to 32 degrees C, enzyme synthesis ceased immediately. After 30 min at 32 degrees C, cells recovered at 20 degrees C after a lag of 30 min. Rifampin and chloramphenicol prevented recovery of synthesis at 20 degrees C. Rifampin-insensitive proteinase synthesis (an indirect measure of proteinase-specific mRNA pools) decreased after the exposure of cells to 32 degrees C for 30 min but was recovered during incubation at 20 degrees C. Controls not exposed to a temperature shift experienced no loss of rifampin-independent synthesis. Cells experienced a 50% reduction in mRNA pools after 15 min at 32 degrees C. The data support the working hypothesis that the loss of mRNA pools after treatment at 32 degrees C is responsible for the lag before the recovery of extracellular proteinase synthesis.

Regulation of alpha-galactosidase synthesis in Saccharomyces cerevisiae and effect of cerulenin on the secretion of this enzyme

Saccharomyces cerevisiae -136ts MEL10 (a thermosensitive mutant whose RNA synthesis is inhibited at 37 degrees C but is normal at 23 degrees C), when grown at 23 degrees C in the presence of galactose, melibiose or L-arabinose, these cells synthesize alpha-galactosidase mRNA. In the simultaneous presence of both galactose and glucose the transcription of alpha-galactosidase mRNA is blocked. Glucose also interferes with mRNA translation, but the degree of inhibition depends on concentration and time of addition of the hexose to induced cells. It has been found that the final concentration of alpha-galactosidase produced by induced cells when transferred at the non-permissive temperature (37 degrees C) is inversely proportional to the incubation time in glucose. Cerulenin inhibits lipid formation on growing yeasts, but protein synthesis and selective permeability are not affected. The antibiotic partially inhibits secretion of alpha-galactosidase with a parallel accumulation of this enzyme in membranous structures, specially at the level of the plasma membrane. Induction of alpha-galactosidase or cerulenin addition to growing cells, results in changes in the polypeptide composition of the plasma membrane.

Polypeptide synthesis during protoplasmic incompatibility in the fungus Podospora anserina

In Podospora anserina, self-lysis resulting from the combination of the R and V incompatibility genes is accompanied by the appearance, in lysing cells, of specific enzyme activities, among which is a laccase exoenzyme, and by a quenching of ribonucleic acid synthesis. Present results show that the occurrence of the laccase is the result of de novo synthesis. By means of two-dimensional gel electrophoresis it was shown that the onset of self-lysis is accompanied by the immediate shut-off of more than 60% of the pre-existing normal polypeptide synthesis and the occurrence of at least 20 new polypeptides. The synthesis of these new polypeptides is active for several hours after the cessation of RNA synthesis, concurrently with the synthesis of about 30 normal polypeptides which is maintained. These modifications of protein synthesis are not accompanied by a concomitant variation in the level of polysomes. It is deduced that incompatibility genes are involved in the control of both transcription and translation.

Peptone induction and rifampin-insensitive collagenase production by Vibrio alginolyticus

Vibrio alginolyticus produces an extracellular collagenase which requires specific induction by collagen or its high-molecular-weight fragments. Peptone also induces collagenase during the late exponential and early stationary growth phases. The peptone inducers have been shown to have a broad molecular weight range between 1,000 and 60,000. The peptone inducers supported slow growth of V. alginolyticus when supplied as the sole nitrogen source in minimal medium. Digestion of the peptone inducers with purified V. alginolyticus collagenase resulted in a decrease in their inducing ability, whereas digestion with trypsin or alpha-chymotrypsin did not. This indicated that induction by the inducers required the presence of collagenase-sensitive bonds. Prolonged digestion of the inducers with collagenase did not completely eliminate the inducing ability of the inducers. The peptone inducers acted as inhibitors of collagenase. A minimal medium induction system has been developed which involves resuspending cells at high density in a medium containing succinate, (NH(4))(2)SO(4), KH(2)PO(4), and the peptone inducer. Cells grown in minimal medium induce earlier than cells grown on peptone, Casamino Acids, or tryptone. Collagenase production was shown to occur for 30 to 60 min in the presence of rifampin at levels which completely inhibit the incorporation of [(3)H]uracil into trichloroacetic acid-precipitable material. Chloramphenicol completely and immediately abolished collagenase production, which together with labeling studies has confirmed that collagenase production involves de novo synthesis of the enzyme. Both glucose and Casamino Acids repressed collagenase production, although synthesis of the enzyme continued for 30 to 60 min after their addition. The repression of collagenase production by glucose and Casamino Acids was more severe than the inhibition of enzyme formation due to addition of rifampin.

Podospora anserina mutant defective in protoperithecium formation, ascospore germination, and cell regeneration

A mutant (modx) was selected on the basis of the suppression of self-lysis due to a recessive mutation (modB). modx, a dominant mutation, reduced hyphal branching from nonapical cells, abolished protoperithecium formation, and induced the death of stationary cells only when these were isolated to obtain further development. Mutant ascospores, formed in the fruiting bodies which occasionally occur under specific conditions (32 degrees C on starved medium), showed a delay in the germination process (up to 3 months instead of about 5 h for wild-type ascospores) when submitted to incubation under standard conditions (26 degrees C on germination medium) and failed to germinate at 18 degrees C. Revertants from modx strains, selected on the basis of the suppression of the nonrenewal of growth from stationary cells, were wild type for all the other three defects. Indirect arguments suggested that the modx mutant strain might be defective in the control of a specific class of stable messenger ribonucleic acids which would be essential for the physiology of ascospores and stationary cells.

Secretion of phospholipase C by Pseudomonas aeruginosa

The conditions necessary for the secretion of phospholipase C (phosphatidylcholine cholinephosphohydrolase) by Pseudomonas aeruginosa were studied. Enzyme secretion by washed cell suspensions required a carbon source and ammonium, potassium, and calcium ions. The calcium requirement could be substituted by magnesium and strontium but not by copper, manganese, cobalt, or zinc. During growth in liquid medium, cells secreted phospholipase C during late logarithmic and early stationary phases. Secretion was repressed by the addition of inorganic phosphate but not by organic phosphates, glucose, or sodium succinate. Studies with tetracycline indicated that de novo protein synthesis was necessary for the secretion of phospholipase C and that the exoenzyme was not released from a preformed periplasmic pool. Similarly, extraction of actively secreting cells with 0.2 M MgCl2 at pH 8.4 solubilized large quantities of the periplasmic enzyme alkaline phosphatase but insignificant amounts of phospholipase C. Bacteria continued to secrete enzyme for nearly 45 min after the addition of inorganic phosphate or rifampin.