Identification of Mutations Associated with Macrofiber Formation in BACILLUS SUBTILIS

A search was made for the genes responsible for the production of helical macrofibers in the original collection of macrofiber-producing strains of B. subtilis. Two loci were identified: fibA, located between hisA and tag-1, and fibB, linked to cysB. fibA governs a short-lived division suppression phenomenon associated with the production of rudimentary fibers, whereas fibB appears to be responsible for a persistent division suppression and a more highly organized helical macrofiber. Both mutations are recovered from each of the original macrofiber-producing strains which also carried the div IV-B1 mutation responsible for minicell production. The latter mutation by itself is not sufficient, however, for the production of macrofibers. Other known mutations leading to division suppression that map in the same region are shown not to be allelic to fibA or fibB. Neither fib locus appears to be responsible for helix hand determination.     

Genetic Analysis of Pleiotropic Negative Sporulation Mutants in Bacillus subtilis

Genetic studies were undertaken on 14 pleiotropic negative sporulation mutants. These mutants (spoA) which are blocked early in the sporulation process were found to map near the terminus of the Bacillus subtilis chromosome in a region enriched in genes involved in spore formation. Two- and three-factor crosses by transduction and transformation led to the conclusion that the pleiotropic spoA mutations formed a linked cluster. The genetic distance across the cluster calculated from transformation data was compatible with the mutant sites defining a single gene. Suppressor studies revealed that either a nonsense or missense mutation in the spoA locus generated a pleiotropic negative phenotype. It was concluded that the locus codes for a protein, and the absence of this protein is responsible for the pleiotropic phenotype.     

Chromosomal Location and Properties of Radiation Sensitivity Mutations in Bacillus subtilis

Transformation and transduction crosses involving recA1, recB2, and urv-1 mutations have shown that these mutations belong to three distinct unlinked genetic loci. The precise position of these loci on the Bacillus subtilis chromosome map has been determined. The behavior of recB2 strains in transformation studies suggested a dominance of recB2(+) function over recB2 and an early expression of this phenotype during transformation. Strains bearing two ultraviolet sensitivity markers possess a phenotype characteristic of the marker with the most adverse effect on recombination. The possibility that the effects of the two mutations are additive was also considered. Results are also presented which show that a phage-induced enzyme is not responsible for the high transducibility of recA1 strains.     

Pleiotropic Effects of Suppressor Mutations in Bacillus subtilis

Isogenic strains of Bacillus subtilis carrying sup-1 (26), sup-3 (10), or their wild-type alleles were constructed in three genetic backgrounds. The patterns of suppression at 37 and 43.5 C, identity of mapping site, effects of the suppressor genes on growth rate, sporulation, and production of altered enzymes were examined. The similarity of the suppression pattern by sup-1 and sup-3 suggests that the suppressors are of the same type. They do not, however, represent mutations in the same gene, since, based on differences in temperature sensitivity of phage mutants in suppressor-containing hosts, sup-1 and sup-3 insert different amino acids and can coexist within the same cell. The ability to produce slow-migrating forms of enzymes of the type described in the accompanying paper was co-transferred with either of the suppressor genes during transformation, was lost on reversion of the suppressor mutations, and was independent of the genetic background. Similarly, transformation and reversion studies indicate that the additional pleiotropic properties such as slow growth rate and inability to attain competence or to yield plaques with phi105C4, which are characteristic of the Okubo sup-1 strain (HA101B) but not its early sporulation defect, result from the presence of the suppressor mutation. The possible mechanisms by which altered enzyme forms and the additional pleiotropic effects are produced in suppressor strains are discussed. In addition, a newly recognized suppressor phenotype is described and partially characterized.     

Genetic Mapping of a Group of Temperature-Sensitive dna Initiation Mutants in BACILLUS SUBTILIS

Recombination frequencies among temperature-sensitive dna mutants from various laboratories were analyzed, and eleven dna mutants were found to be closely linked. They are classified as group B dna mutants, since these are closely linked with dnaB19, originally isolated and approximately mapped near leuA8 by KARAMATA and GROSS (1970). However, the dnaB19 mutation itself has relatively high recombination frequencies with the other mutations, thus, we propose to subdivide the dnaB group into two subgroups--dnaBI, including ten mutants (dna-1, dna-3, dna-5, dna-17, dna-27, dna-51, dna-60, dna-62, dna-103 and dna-134) and dnaBII, including dnaB19. The map order of dnaB and markers in the vicinity was determined to be argA-citH-citC-phoP-PhoR-polA-dnaBI-dnaBII-citF-leuA-pheA.     

对一个玉米双重标记新突变基因（os）的染色体定位和初步遗传研究

利用一套１６个玉米Ｂ－Ａ染色体易位的系列材料,和一套１１个由ｗｘ基因标记易位断点的第９染色体相互易位材料,测定了一个新发现的玉米隐性突变基因ｏｓ（ｏｐａｑｕｅ－ｓｍａｌｌ ｇｅｒｍ）所属的染色体。两个结果相互印证,证明该基因位于第２染色体短壁。ｏｓ基因具有产生不透明胚乳和小胚面的双重遗传效应,是一个良好的遗传标记。这一特性有可能来检查异雄核受精或定向受精的存在和比数。ｏｓ基因除缩小种胚体积之外,也     

New Loci in DICTYOSTELIUM DISCOIDEUM Determining Pigment Formation and Growth on BACILLUS SUBTILIS

Seventeen independently isolated pigmentless (white) mutations in Dictyostelium discoideum are all recessive and fall into three complementation groups identifying two new whi loci in addition to the previously characterized whiA locus. whiB and whiC map to linkage groups III and IV, respectively. In addition, it was discovered that our laboratory stock of NC4, the wild-type strain from which these mutants were derived, has spontaneously lost the ability to grow on Bacillus subtilis. This new mutation, bsgB500, maps to linkage group VII and is not allelic to bsgA. bsgB500 is the first spontaneously derived mutation in D. discoideum that can be used to select heterozygous diploids, and for the first time allows genetic analysis to be routinely performed on strains derived from an unmutagenized background.     

Transposition of the Arsenate Resistance Locus of BACILLUS SUBTILIS Strains 23 and 168

Wild-type Bacillus subtilis strains 23 and 168 are resistant to high concentrations of sodium arsenate. The genetic configurations of the arsenate resistance loci of these two related strains of B. subtilis have been characterized. The transformable 168 strain has a single resistance locus which maps between phe and aroD in the terminal third of the genome. In contrast, strain 23 is shown to have its single arsenate resistance locus between purB and thr in the first third of the bacterial chromosome. Moreover, in strain 23 the chromosomal segment equivalent to the phe-linked asa region of 168 strains is missing. DNA isolated from 23 strains is able to transform 168 arsenate-sensitive strains to resistance and the heterologous 23 DNA is found to preferentially establish a new purB linked asa locus in such transformed cells. Thus, the majority of phenotypically arsenate-resistant cells recovered after exposure of competent 168 sensitive mutants to 23 DNA are "heterozygous" and still retain their phe-linked mutated asa locus. The tolerance of several of these heterologously transformed hybrid strains to arsenate suggests that the 168 and 23 asa gene products are similar, and a transposition model for the evolution of arsenate resistance in B. subtilis is proposed.     

Congression of Unlinked Markers and Genetic Mapping in the Transformation of BACILLUS SUBTILIS 168

A thorough examination of cotransformation of two unlinked genetic markers in Bacillus subtilis 168 shows that the two recombinational events do not occur randomly. The cotransformation frequency is dependent on the distance between the two markers as well as on the order in which they replicate in the competent cell. These results indicate that uptake and/or integration of DNA molecules bearing these genetic markers is enhanced at the time these markers replicate in the competent cell.     

Carbohydrate Accumulation and Metabolism in Escherichia coli: the Close Linkage and Chromosomal Location of ctr Mutations

Six pleiotropic ctr mutations of Escherichia coli, affecting the ability to utilize 10 carbohydrates, were found to be closely linked to one another and to the mutation of strain MM6 causing lack of enzyme 1 of the phosphotransferase system. These mutations are located at 46 to 47 min on the E. coli map. Preliminary biochemical evidence indicates that the ctr mutants also lack enzyme 1, although they have a different phenotype from MM6.     

Mating Type and Sporulation in Yeast I. Mutations Which Alter Mating-Type Control over Sporulation

In Saccharomyces cerevisiae, meiosis and spore formation as well as mating are controlled by mating-type genes. Diploids heterozygous for mating type (aα) can sporulate but cannot mate; homozygous aa and αα diploids can mate, but cannot sporulate. From an αα diploid parental strain, we have isolated mutants which have gained the ability to sporulate. Those mutants which continue to mate as αα cells have been designated CSP (control of sporulation). Upon sporulation, CSP mutants yield asci containing 4α spores. The mutant gene which allows αα cells to sporulate is unlinked to the mating-type locus and also acts to permit sporulation in aa diploid cells. Segregation data from crosses between mutant αα and wild-type aa diploids and vice versa indicate (for all but one mutant) that the mutation which allows constitutive sporulation (CSP) is dominant over the wild-type allele. Some of the CSP mutants are temperature-sensitive, sporulating at 32°, but not at 23°. In addition to CSP mutants, our mutagenesis and screening procedure led to the isolation of mutants which sporulate by virtue of a change in the mating-type locus itself, resulting in loss of ability to mate.     

Identification and Characterization of Mutations Affecting Sporulation in Saccharomyces Cerevisiae

Mutations affecting the synthesis of the sporulation amyloglucosidase were isolated in a homothallic strain of Saccharomyces cerevisiae, SCMS7-1. Two were found, both of which were deficient in sporulation at 34 degrees. One, SL484, sporulated to 50% normal levels at 30 degrees but less than 5% at 34 degrees or 22 degrees. The other, SL641, failed to sporulate at any temperature. Both mutants were blocked before premeiotic DNA synthesis, and both complemented spo1, spo3, and spo7. Genetic analysis of the mutation in SL484 indicated linkage to TRP5 and placed the gene 10 map units from TRP5 on chromosome VII. A plasmid containing an insert which complements the mutation in SL484 fails to complement SL641. We therefore conclude that these two mutations are in separate genes and we propose to call these genes SPO17 and SPO18. These two genes are (with SPO7, SPO8, and SPO9) among the earliest identified in the sporulation pathway and may interact directly with the positive and negative regulators RME and IME.