Synchronous cultures of Bacillus subtilis obtained by filtration with glass fiber filters

The product of the yvoC (gerF) gene of Bacillus subtilis is required for spore germination

All known gerF mutations affecting Bacillus subtilis spore germination have been mapped, by a combination of recombination and complementation analysis, to yvoC (Igt), a gene belonging to the yvoB (ptsK) yvoC (Igt) yvoDEF operon. Examination of the properties of null mutants confirmed that the only gene in the operon that affects germination is yvoC, which encodes a homologue of known prelipoprotein diacylglyceryl transferases. As several germination proteins (GerAC, GerBC, GerKC, GerD) are predicted lipoproteins, it is not unreasonable to assume that a defect in prelipoprotein processing will affect spore germination. Two other null mutants in this chromosomal region showed a clear phenotype: the nagA gene is required for growth on N-acetylglucosamine, whereas a null mutation in yvoB (ptsK) affects colony formation from single cells.

A 35.7 kb DNA fragment from the Bacillus subtilis chromosome containing a putative 12.3 kb operon involved in hexuronate catabolism and a perfectly symmetrical hypothetical catabolite-responsive element

The Bacillus subtilis strain 168 chromosomal region extending from 109 degrees to 112 degrees has been sequenced. Among the 35 ORFs identified, cotT and rapA were the only genes that had been previously mapped and sequenced. Out of ten ORFs belonging to a single putative transcription unit, seven are probably involved in hexuronate catabolism. Their sequences are homologous to Escherichia coli genes exuT, uidB, uxaA, uxaB, uxaC, uxuA and uxuB, which are all required for the uptake of free D-glucuronate, D-galacturonate and beta-glucuronide, and their transformation into glyceraldehyde 3-phosphate and pyruvate via 2-keto-3-deoxygluconate. The remaining three ORFs encode two dehydrogenases and a transcriptional regulator. The operon is preceded by a putative catabolite-responsive element (CRE), located between a hypothetical promoter and the RBS of the first gene. This element, the longest and the only so far described that is fully symmetrical, consists of a 26 bp palindrome matching the theoretical B. subtilis CRE sequence. The remaining predicted amino acid sequences that share homologies with other proteins comprise: a cytochrome P-450, a glycosyltransferase, an ATP-binding cassette transporter, a protein similar to the formate dehydrogenase alpha-subunit (FdhA), protein similar to NADH dehydrogenases, and three homologues of polypeptides that have undefined functions.

Autolysins and shape change in rodA mutants of Bacillus subtilis

The biochemical phenotype of rodA mutants was not affected by the simultaneous presence in double mutants of the lyt gene which makes them 90 to 95% deficient in autolysin action. The only morphological effect of this deficiency on the expression of the rod gene was that both the rod and the coccal forms of the mutant failed to separate and grew as long chains of cells. Inhibition of protein synthesis stopped the increase in peptidoglycan that occurred when the growth temperature for the mutants was raised to 45 degrees C. These observations support the idea that a derepression of peptidoglycan synthesis occurs at this temperature. The increased amount of cellular peptidoglycan at the higher growth temperature is not likely to be the result of the concomitant switching off of autolytic enzyme action.

Study of pole assembly in Bacillus subtilis by computer reconstruction of septal growth zones seen in central, longitudinal thin sections of cells

The septal growth of Bacillus subtilis 168/s has been studied by making a number of observations from thin sections of cells from exponentially growing cultures. The process was initiated by the formation of a new cross wall under a preexisting layer of cylindrical wall. An annular notch appeared to cut through the overlying wall and presumably allowed the cross wall to split into two layers of peripheral wall. During this initial notching process, two raised bands of wall material were produced which resembled those previously observed in morphological studies of Streptococcus faecalis. Through an improved fixation technique, it was possible to preserve the bands seen in B. subtilis to the extent that they were used as markers to study the subsequent stages of septal growth. These stages included (i) the continued displacement of the two bands from the cross wall (as the two nascent polar surfaces enlarged and as the diameter of the cross wall decreased), (ii) the closure of the cross wall, and (iii) the final severance of the common cross wall connection between two completed poles. To study this process in a more quantitative manner, three-dimensional reconstructions of the envelope observed between pairs of the raised bands were made from axial thin sections of cells. The process of reconstruction was based on a technique by which x, y coordinates were taken from thin sections and were rotated around the cell's central axis. These reconstructions were used to estimate the surface area or volume of the reconstructed zones or their parts. A round of septal growth was then simulated by arranging 118 reconstructions in order of increasing surface area or volume. The topology of the process was studied by noting how various measurements of septal thickness, length, surface area, and volume varied as a function of increasing septal zone size. This analysis was based on several assumptions, of which three of the most important are: (i) the bands produced by the initial notching process are markers which separate septal from cylindrical wall growth; (ii) a septal zone observed between pairs of bands is made up of two nascent poles and a single cross wall; and (iii) as septal zones develop in terms of relative age they increase in size (volume or surface area) or amount of wall. The data suggested that the S. faecalis model of surface growth (in which polar growth occurs through a regulated constrictive separation and expansion of a cross wall) also seems applicable to the pattern of septal growth observed here for B. subtilis. This was indicated from measurements which showed that increases in the size of nascent polar surfaces were correlated with decreases in cross wall diameter. An explanation of these observations may be that decreases in cross wall diameter were due to a progressive splitting of the cross wall that removed surface from the outer circumference of the cross wall and converted it into new polar surface. Calculations further suggested that if the poles of B. subtilis were made by this model a sizeable and variable increase in surface area of the cross wall would also be required to convert these separating cross wall layers into two curved polar structures. Measurements of wall thickness taken from various locations within septal zones indicated that while the thickness of the polar wall of B. subtilis was constant over its surface, the width of the cross wall varied considerably during a round of synthesis. Again, one of the simplest explanations compatible with these observations and those previously made in S. faecalis is that the B. subtilis cross wall is brought to a constant thickness (possibly by remodeling or precursor addition) before or during separation. Although most observations made from the reconstruction of the septal zones of B. subtilis may fit the S. faecalis model of surface growth, differences in the pattern of septal growth were seen when the two organisms were compared. These have been discussed in terms of differences in the regulation of their respective septal growth sites and basic mechanisms of wall assembly and modification.

Macromolecular synthesis in chromosome initiation mutants of Bacillus subtilis

Inactivation of the dna B or dna D gene product in Bacillus subtilis stimulates RNA and protein synthesis. Strains containing ts dna B and D mutations have been constructed by introducing the mutations by transformation into a thymine requiring strain which does not lyse during thymine starvation. The consequences of inactivation of these gene products have been assessed by comparing RNA and protein synthesis during thymine starvation at the restrictive temperature with the recipient strain. In the ts+ strain, there is a doubling in rate of RNA synthesis during thymine starvation. In the ts dna B and D mutations at the restrictive temperature the rate of RNA synthesis increases four fold. By preincubating the mutants in the absence of thymine for one generation at the permissive temperature the two fold increase in rate of RNA synthesis associated with inactivation of the initiation complex can be demonstrated under conditions where the ts+ strain shows a decrease in rate of RNA synthesis. The rate of protein synthesis observed largely reflects the rate of RNA synthesis in all strains. Completion of the chromosome at the restrictive temperature has no significant effect on the rate of RNA synthesis. It is suggested that inactivation of the initiation complex after chromosome initiation could play an important role in control of RNA synthesis in relation to the cell cycle.

Morphogenesis and differentiation in Rhodomicrobium vannielii and other budding and prosthecate bacteria

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Prophage mutation causing heat inducibility of defective Bacillus subtilis bacteriophage PBSX

A mutant of Bacillus subtilis 168 has been isolated in which the defective phage PBSX was heat inducible, whereas another phage, phi105, was not so induced. A culture of the mutant grown at 30 degrees C, when shifted to 45 degrees C, began to lyse after 45 min; cell viability began to decrease after 10 min. Heat-induced lysis of the mutant was prevented by chloramphenicol. DNA, RNA, protein, and peptidoglycan synthesis were normal at the nonpermissive temperature up to the time of lysis. The site of xhi-1479 mutation causing this phenotype was linked (50%) in phage PBS1-mediated transduction to the host marker metC and to another PBSX marker xtl and was thus thought to map within the PBSX prophage. The order of markers was argC-thiB-metA-xhi-metC. The xhi mutation was thus distinct from another mutation, tsi-23, causing a similar heat inducibility of PBSX (Siegel and Marmur, 1969), which was unlinked to the metC marker. tsi-23 is therefore thought to be a host mutation, and the available evidence for a scattered phage genome being the cause of the defective nature of PBSX is thus less tenable. It was shown that the mutant, besides carrying the xhi mutation, also carried another closely linked mutation, xki-1479, which caused the PBSX produced to have no killing activity on the sensitive strain W23. The xki mutation was separated from xhi by recombination.

Autolytic enzyme-deficient mutants of Bacillus subtilis 168

Mutants of Bacillus subtilis strain 168 have been isolated that are at least 90 to 95% deficient in the autolytic enzymes N-acetylmuramyl-L-alanine amidase and endo-beta-N-acetylglucosaminidase. These mutants grow at normal rates as very long chains of unseparated cells. The length of the chains is directly related to the growth rates. They are nonmotile and have no flagella, but otherwise appear to have normal cell morphology. Their walls are fully sysceptible to enzymes formed by the wild type and have the same chemical composition as the latter. Cell wall preparations from the mutants lyse at about 10% of the rate of those from the isogenic wild type, with the correspondingly small liberation of both the amino groups of alanine at pH 8.0 and of reducing groups at pH 5.6. Likewise, Microcococcus luteus walls at pH 5.6 and B. subtilis walls at pH 8 are lysed only very slowly by LiCl extracts made from the mutants as compared with rates obtained with wild-type extracts. Thus, the activity of both autolytic enzymes in the mutants is depressed. The frequencies of transformation, the isolation of revertants, and observations with a temperature-sensitive mutant all point to the likelihood that the pleiotropic, phenotypic properties of the strains are due to a single mutation. The mutants did not produce more protease or amylase than did the wild type. They sporulate and the spores germinate normally. The addition of antibiotics to exponentially growing cultures prevents wall synthesis but leads to less lysis than is obtained with the wild type. The bacteriophage PBSX can be induced in the mutants by treatment with mitomycin C.

Magnesium and anion requirements of rodB mutants of Bacillus subtilis

rodB mutants of Bacillus subtilis have been found to require several hundred-fold more Mg2+ in a minimal growth medium than the wild type to achieve rapid growth. In the presence of all concentrations of Cl-, the organisms grow as deformed cocci, but with 10 mM Mg2+ and Br-, I-, or NO3- present they grow as rods. The morphology is then directly under the control of the concentration of both Mg2+ and anion. Originally, it was found that L-glutamic acid in the medium brought about the change from deformed spheres to rods. This amino acid will similarly function at a much lower concentration when the higher concentrations of Mg2+ and Cl- are also present. At a constant concentration of L-glutamate, the morphology can be controlled by varying the Mg2+ concentration. In the presence of Mg2+ and I-, the morphological change is temperature sensitive. At 30 C rods are formed and at 42 C deformed cocci are formed. The requirement of a rodB mutant for a high concentration of magnesium and the round morphology have been shown to be most probably due to a single mutation.

Control of membrane protein synthesis in Bacillus subtilis

In synchronous cultures of Bacillus subtilis 168/S grown on succinate as a sole carbon source (mean generation time 115 min), chromosome initiation occurs at the beginning of the cell cycle but the rate of membrane protein synthesis doubles in mid-cycle more or less coincident with nuclear segregation. In glucose-grown cultures, the doubling in rate of membrane protein synthesis occurs at about the same time as nuclear segregation and DNA initiation at the beginning of the cycle. Control of the rate of membrane synthesis by the chromosome has been demonstrated by inhibiting DNA synthesis using thymine starvation and showing that membrane protein synthesis continues at a constant rate, whereas the rate of cytoplasmic protein synthesis almost doubles. I suggest that the replication of a region at or close to the chromosome terminus is required to allow the doubling in rate of membrane synthesis.

Anucleate cell production and surface extension in a temperature-sensitive chromosome initiation mutant of Bacillus subtilis

At 45 C, in a temperature-sensitive initiation mutant (TsB134) of Bacillus subtilis 168 Thy- tryp-, growing in a glucose-arginine minimal medium, chromosome completion occurred over a period of 80 to 90 min, after which there was no further nuclear division. Normal symmetrical cell divisions continued for a generation afterwards, so that nuclei were segregated into separate cells. During this period asymmetric divisions started to occur. Septa appeared at 25 to 30% from one end of the cell, giving a small anucleate cell and a larger nucleate cell. During inhibition of deoxyribonucleic acid (DNA) synthesis by thymine starvation under the restrictive conditions, asymmetrical division also occurred until there was approximately one nucleus per cell (about one generation time). Asymmetric division, giving anucleate cells, then occurred. Similar results were obtained when DNA synthesis was inhibited by nalidixic acid. After 3 h at 45 C, the rate of anucleate cell production in the presence and absence of thymine was constant at one division per 85 min per chromosome terminus present when DNA synthesis stopped. In the absence of DNA synthesis (during thymine starvation) at 35 C, growth in cell length was linear (i.e., the rate was constant), but at 45 C during thymine starvation the rate gradually increased by more than twofold. It is suggested that this was due to the establishment of new sites of growth associated with anucleate cell production. In the presence of thymine at 45 C, the rate of length extension increased by more than fourfold, which it is suggested was caused by the appearance of new growth zones as a result of chromosome termination and a contribution associated with anucleate cell production. If the mutant was incubated at 45 C for 90 min, both in the presence and absence of thymine, then anucleate cell formation could continue on restoration to 35 C in the absence of thymine...

Control of cell length in Bacillus subtilis

During inhibition of deoxyribonucleic acid synthesis in Bacillus subtilis 168 Thy-minus Tryp-minus, the rate of length extension is constant. A nutritional shift-up during thymine starvation causes an acceleration in the linear rate of length extension. During a nutritional shift-up in the presence of thymine, the rate of length extension gradually increases, reaching a new steady state at about 50 min before the new steady-state rate of cell division is reached. The steady-state rates of nuclear division and length extension are reached at approximately the same time. The ratio of average cell length to numbers of nuclei per cell in exponential cultures is constant over a fourfold range of growth rates. These observations are consistent with: (i) surface growth zones which operate at a constant rate of length extension under any one growth condition, but which operate at an absolute rate proportional to the growth rate of the culture, (ii) a doubling in number of growth zones at nuclear segregation, and (iii) a requirement for deoxyribonucleic acid replication for the doubling in a number of sites.