The synthesis of polyglutamic acid (PGA) was repressed by exogenous glutamate in strains of Bacillus licheniformis but not in strains of Bacillus subtilis, indicating a clear difference in the regulation of synthesis of capsular slime in these two species. Although extracellular γ-glutamyltranspeptidase (GGT) activity was always present in PGA-producing cultures of B. licheniformis under various growth conditions, there was no correlation between the quantity of PGA and enzyme activity. Moreover, the synthesis of PGA in the absence of detectable GGT activity in B. subtilis S317 indicated that this enzyme was not involved in PGA biosynthesis in this bacterium. Glutamate repression of PGA biosynthesis may offer a simple means of preventing unwanted slime production in industrial fermentations using B. licheniformis.
Microcycle sporogenesis induced in Bacillus cereus T by phosphate limitation occurs over a narrow range of phosphate to spore inoculum ratios. Sufficient phosphate is required to satisfy the demands for a twofold increase in deoxyribonucleic acid; net ribonucleic acid synthesis is not required. The total ribonucleic acid content of the culture was variable, and deoxyribonucleic acid synthesis was restricted to a twofold increase. Developmental changes during outgrowth occurred synchronously, whereas enzyme synthesis was periodic. The timing of the synthesis of tricarboxylic cycle enzymes, extracellular protease, arginase, histidase, and alkaline phosphatase was measured. Histidase could be induced after 2.5 hr throughout microcycle sporogenesis. Several other features of macromolecular synthesis during microcycle sporogenesis are described. Differences between this pattern and those observed during outgrowth leading to cell division are discussed. A technique for accurately estimating the levels and time of synthesis of incompletely extractable, labile enzymes is also presented.
The distribution of the extracellular enzyme, thiaminase I, was determined for logarithmically growing cultures of Bacillus thiaminolyticus. About 60% of the enzyme is associated with the cells throughout the growth cycle. The remainder of the enzyme is in the culture medium. The release of the cell-bound thiaminase I is examined under a variety of conditions. The rate and extent of release is dependent on the pH and the nature of the incubation solution. The release process appears to be relatively independent of de novo protein synthesis, energy derived from oxidative phosphorylation, or divalent metal ions. The absence of carbon or nitrogen sources has little effect on the release of the enzyme. Cell-bound thiaminase I probably is the immediate precursor for extracellular thiaminase I found in the culture medium. Washed cells continue to release thiaminase I at the expense of cell-bound enzyme. In addition, purified cell-bound thiaminase I is indistinguishable from purified extracellular thiaminase I by a number of physical and kinetic criteria.
The formation of penicillinase by cultures of Bacillus licheniformis was preferentially suppressed by cerulenin, an antibiotic known to specifically inhibit fatty acid synthesis in microorganisms. The effect was studied at cerulenin concentrations that had almost no effect on the rate of cell growth and overall protein synthesis, but that reduced the rate of [14C]acetate incorporation (by 50 to 70%), indicating partial inhibition of lipid synthesis. The levels of both the released enzyme (exopenicillinase) and its cell-bound precursor were reduced to the same extent (70% to 80%). Enzyme formation was gradually resumed after the removal of cerulenin or the addition of a mixture of fatty acids prepared from lipids extracted from B. licheniformis. Reversal was less effective as the time interval between treatment with cerulenin and addition of fatty acids increased. We conclude that de novo synthesis of fatty acids is required for the formation of both the membrane-bound and extracellular penicillinase. Suppression of the membrane-bound enzyme is a likely consequence of the altered membrane (decreased lipid-to-lipid ratio and increased density) seen in cerulenin-treated preparations. The corresponding suppression of exopenicillinase is consistent with the view that it is derived from the membrane-bound form. A mechanism linking the general class of exportable proteins to specific aspects of lipid synthesis is discussed.
Nine bacterial strains growing on inulin as the sole carbon and energy source were isolated from soil samples by enrichment culture on a mineral medium. Four of the strains were thermophilic and belong to the genus Bacillus. The thermophilic strains synthesized a β-fructosidase that was active on both inulin and sucrose. The presence of inulin in the culture medium is necessary for enzyme synthesis. Most of the activity on inulin was recovered in the culture medium, and the enzyme was synthesized during cell growth.
Bacillus amyloliquefaciens BaM-2 produces large amounts of extracellular enzymes, and the synthesis of these proteins appears to be dependent upon abnormal ribonucleic acid metabolism. A polynucleotide phosphorylase (nucleoside diphosphate:polynucleotide nucleotidyl transferase) was identified, purified, and characterized from this strain. The purification scheme involved cell disruption, phase partitioning, differential (NH4)2SO4 solubilities, agarose gel filtration, and diethylaminoethyl-Sephadex chromatography. The purified enzyme demonstrated the reactions characteristic of polynucleotide phosphorylase: polymerization, phosphorolysis, and inorganic phosphate exchange with the beta-phosphate of a nucleotide diphosphate. The enzyme was apparently primer independent and required a divalent cation. The reactions for the synthesis of the homopolyribonucleotides, (A)n and (G)n, were optimized with respect to pH and divalent cation concentration. The enzyme is sensitive to inhibition by phosphate ion and heparin and is partially inhibited by rifamycin SV and synthetic polynucleotides.
Bacillus subtilis B secretes an inducible, extracellular enzyme, levansucrase. Inhibition studies were undertaken to investigate the possible mechanism of release of this enzyme. The antibiotic cerulenin, at a concentration of 10 micrograms/ml, totally inhibited de novo lipid synthesis in B. subtilis B for at least 1 h, while only slightly reducing protein and RNA synthesis. At this concentration cerulenin, added concomitantly with the inducer sucrose, prevented the release of levansucrase for at least 150 min. This was not due to the prevention of inducer uptake by the cells. The release of the enzyme was also independent of cell division. In B. subtilis 1007 the induction of beta-galactosidase by 5 mM lactose was not prevented by cerulenin. Preliminary evidence indicated the association of a lipid moiety with the enzyme as it passes through the cytoplasmic membrane. Quinacrine (0.2 mM), which inhibits the penicillinase-releasing protease of Bacillus licheniformis, inhibited levansucrase release from B. subtilis B, but had no effect on lipid synthesis.
Washed-cell suspensions of Bacillus amyloliquefaciens secrete significant amounts of the extracellular enzymes alpha-amylase and protease for about 15 min in the almost complete absence of protein synthesis. This apparently represents release of preformed enzyme en route to secretion. The release was independent of energy but was affected by temperature. Pulse-labeling experiments showed that newly synthesized enzyme molecules are either immediately released into the external medium or equilibrate with the preformed enzyme prior to eventual secretion. The results are compatible with a model of secretion whereby enzyme molecules emerging from the cell membrane become temporarily restricted by the cell wall so that a small pool of active enzyme accumulates in this region.
The level of extracellular α-amylase (EC 22.214.171.124) of Bacillus subtilis Marburg was increased about fivefold by introducing the amyR marker from B. natto 1212 through transformation. amyR2 of B. natto 1212 has been assumed to determine a high level of α-amylase of the organism. The gene acts specifically on α-amylase synthesis but not on the production of other extracellular enzymes. α-Amylase of an amyR2-carrying strain was found to be quite similar to that of an isogenic amyR1-carrying strain in the thermostability and electrophoretic behavior of whichever amylase the strain produces. Marburg-type α-amylase (amyEm) or B. natto-α-amylase (amyEn). Anti-amylase serum titration indicates that a high level of the enzyme activity in the amyR2-carrying strain is caused by the existence of more enzyme rather than the presence of an enzyme having higher efficiency. This is supported further by the fact that amyR controls the synthesis of the amyE gene product in mutant M9, which synthesizes a temperature-sensitive-α-amylase, and in mutant M07, which secretes cross-reacting material. The results indicate that amyR regulates the rate of α-amylase synthesis.
Bacillus species produce extracellular, surface-active lipopeptides such as surfactin that have wide applications in industry and medicine. The steps involved in the synthesis of 3-hydroxyacyl-coenzyme A (CoA) substrates needed for surfactin biosynthesis are not understood. Cell-free extracts of Bacillus subtilis strain OKB105 synthesized lipopeptide biosurfactants in presence of l-amino acids, myristic acid, coenzyme A, ATP, and H2O2, which suggested that 3-hydroxylation occurs prior to CoA ligation of the long chain fatty acids (LCFAs). We hypothesized that YbdT, a cytochrome P450 enzyme known to beta-hydroxylate LCFAs, functions to form 3-hydroxy fatty acids for lipopeptide biosynthesis. An in-frame mutation of ybdT was constructed and the resulting mutant strain (NHY1) produced predominantly non-hydroxylated lipopeptide with diminished biosurfactant and beta-hemolytic activities. Mass spectrometry showed that 95.6% of the fatty acids in the NHY1 biosurfactant were non-hydroxylated compared to only ∼61% in the OKB105 biosurfactant. Cell-free extracts of the NHY1 synthesized surfactin containing 3-hydroxymyristic acid from 3-hydroxymyristoyl-CoA at a specific activity similar to that of the wild type (17 ± 2 versus 17.4 ± 6 ng biosurfactant min−1·ng·protein−1, respectively). These results showed that the mutation did not affect any function needed to synthesize surfactin once the 3-hydroxyacyl-CoA substrate was formed and that YbdT functions to supply 3-hydroxy fatty acid for surfactin biosynthesis. The fact that YbdT is a peroxidase could explain why biosurfactant production is rarely observed in anaerobically grown Bacillus species. Manipulation of LCFA specificity of YbdT could provide a new route to produce biosurfactants with activities tailored to specific functions.
cytochrome P450; YbdT; long chain fatty acids; beta hydroxylation; Bacillus subtilis; surfactin
Extracellular polysaccharides are major immunogenic components of the bacterial cell envelope. However, little is known about their biosynthesis in the genus Acinetobacter, which includes A. baumannii, an important nosocomial pathogen. Whether Acinetobacter sp. produce a capsule or a lipopolysaccharide carrying an O antigen or both is not resolved. To explore these issues, genes involved in the synthesis of complex polysaccharides were located in 10 complete A. baumannii genome sequences, and the function of each of their products was predicted via comparison to enzymes with a known function. The absence of a gene encoding a WaaL ligase, required to link the carbohydrate polymer to the lipid A-core oligosaccharide (lipooligosaccharide) forming lipopolysaccharide, suggests that only a capsule is produced. Nine distinct arrangements of a large capsule biosynthesis locus, designated KL1 to KL9, were found in the genomes. Three forms of a second, smaller variable locus, likely to be required for synthesis of the outer core of the lipid A-core moiety, were designated OCL1 to OCL3 and also annotated. Each K locus includes genes for capsule export as well as genes for synthesis of activated sugar precursors, and for glycosyltransfer, glycan modification and oligosaccharide repeat-unit processing. The K loci all include the export genes at one end and genes for synthesis of common sugar precursors at the other, with a highly variable region that includes the remaining genes in between. Five different capsule loci, KL2, KL6, KL7, KL8 and KL9 were detected in multiply antibiotic resistant isolates belonging to global clone 2, and two other loci, KL1 and KL4, in global clone 1. This indicates that this region is being substituted repeatedly in multiply antibiotic resistant isolates from these clones.
The unusual thermolability of glyceraldehyde-3-phosphate dehydrogenase from the facultative thermophile Bacillus coagulans KU (Crabb et al., Biochemistry 16:4840-4847, 1977) has provided the first opportunity to study a homologous enzyme from the same genus that exhibits a marked difference in thermostability. In pursuit of the structural bases for the thermostability of proteins, the sequences of the amino terminus (residues 1 through 27) and the active-site cysteine cyanogen bromide peptide (residues 130 through 167) of this enzyme have been determined and compared with sequences of the enzyme from other sources. The importance of comparing phylogenetically related proteins is evident from the 87% identity found between these sequences in the enzyme from B. coagulans and Bacillus stearothermophilus, versus only 45% identity for all other known sequences. The marked sequence identity of the enzyme from the two Bacillus species drew attention to the variable region (residues 138 through 140a) which is exposed to the exterior of the quaternary structure of this enzyme. Based on the reported crystallographic structures of the enzyme from lobster muscle and B. stearothermophilus and space-filling models of the variable region, the segment Asp-Pro-Lys-Ala in B. stearothermophilus should be more thermostable than the analogous sequence, Asp-Ala-Ala-Asn, from B. coagulans. In addition, the space-filling models suggested that the spatial relationship of an amino acid side chain and its potential for close packing and interactions with neighboring side chains may be more important than the type of amino acid substituted.
Many bacteria inhibit motility concomitant with the synthesis of an extracellular polysaccharide matrix and the formation of biofilm aggregates. In Bacillus subtilis biofilms, motility is inhibited by EpsE, which acts as a clutch on the flagella rotor to inhibit motility, and which is encoded within the 15 gene eps operon required for EPS production. EpsE shows sequence similarity to the glycosyltransferase family of enzymes, and we demonstrate that the conserved active site motif is required for EPS biosynthesis. We also screen for residues specifically required for either clutch or enzymatic activity and demonstrate that the two functions are genetically separable. Finally, we show that, whereas EPS synthesis activity is dominant for biofilm formation, both functions of EpsE synergize to stabilize cell aggregates and relieve selective pressure to abolish motility by genetic mutation. Thus, the transition from motility to biofilm formation may be governed by a single bifunctional enzyme.
Bacteria form persistent and antibiotic-resistant cell aggregates known as biofilms. Biofilms can form in environmental settings on plant and animal tissues, in industrial settings on pipes and the hulls of ships, and in clinical settings on catheters and medical devices. Biofilms are characterized by two features: the cells within the aggregates are non-motile, and they produce an extracellular polysaccharide (EPS) matrix. We have found a bifunctional enzyme EpsE that contributes to both features of biofilm formation in Bacillus subtilis. EpsE interacts with the flagella rotor to inhibit motility and also cooperates with other enzymes to synthesize the EPS matrix. Thus, the transition from motility to biofilm formation may be governed by a single bifunctional protein. In the past decade, research on biofilms has been focused on biofilm eradication. Understanding how cells transition into the biofilm state may provide additional approaches of preventing the formation of a biofilm in the first place.
In Bacillus subtilis, the extracellular enzyme levansurcrase is synthesized in the presence of sucrose. A termination structure between the transcription start site and the structural gene was the apparent site for regulation by sucrose of transcription into the structural gene. Sequence analysis of the sacB leader region from two strains constitutive for levansucrase synthesis showed a single base change in the stem of this termination structure. This single base change also led to the constitutive synthesis of a sacB'-'lacZ fusion, whereas the wild-type sacB'-'lacZ fusion was induced by the addition of sucrose. S1 nuclease mapping of sacB transcripts with probes labeled either within the termination structure or 3' to the termination structure showed that sucrose did not increase the number of transcripts extending into the termination structure; however, sucrose did increase the number of transcripts extending past the termination structure. Two pleiotropic mutations which affect the expression of levansucrase, sacQ36 hyperproducing [sacQ36(Hy)] and sacU32(Hy), were separately introduced into the strain carrying the sacB'-'lacZ fusion. These mutations each increased the expression levels of the sacB'-'lacZ fusion. S1 mapping showed increased levels of transcript initiating at the sacB promoter in strains with the sacQ36(Hy) and sacU32(Hy) mutations. This increased transcription appeared to be independent of the sucrose-regulated transcription termination, suggesting the existence of at least two different mechanisms for the regulation of sacB expression.
This study was performed to determine whether extracellular silver nanoparticles (AgNPs) production is a genus-wide phenotype associated with all the members of genus Morganella, or only Morganella morganii RP-42 isolate is able to synthesize extracellular Ag nanoparticles. To undertake this study, all the available Morganella isolates were exposed to Ag+ ions, and the obtained nanoproducts were thoroughly analyzed using physico-chemical characterization tools such as transmission electron microscopy (TEM), UV-visible spectrophotometry (UV-vis), and X-ray diffraction (XRD) analysis. It was identified that extracellular biosynthesis of crystalline silver nanoparticles is a unique biochemical character of all the members of genus Morganella, which was found independent of environmental changes. Significantly, the inability of other closely related members of the family Enterobacteriaceae towards AgNPs synthesis strongly suggests that AgNPs synthesis in the presence of Ag+ ions is a phenotypic character that is uniquely associated with genus Morganella.
Bacteria in the genus Bacillus are the source of several enzymes of current industrial interest. Hydrolases, such as amylases, proteases, and lipases, are the main enzymes consumed worldwide and have applications in a wide range of products and industrial processes. Fermentation processes by Bacillus subtilis using cassava wastewater as a substrate are reported in the technical literature; however, the same combination of microorganisms and this culture medium is limited or nonexistent. In this paper, the amylase, protease, and lipase production of ten Bacillus subtilis strains previously identified as biosurfactant producers in cassava wastewater was evaluated. The LB1a and LB5a strains were selected for analysis using a synthetic medium and cassava wastewater and were identified as good enzyme producers, especially of amylases and proteases. In addition, the enzymatic activity results indicate that cassava wastewater was better than the synthetic medium for the induction of these enzymes.
The Bacillus subtilis genome-reduced strain MGB874 exhibits enhanced production of exogenous extracellular enzymes under batch fermentation conditions. We predicted that deletion of the gene for RocG, a bi-functional protein that acts as a glutamate dehydrogenase and an indirect repressor of glutamate synthesis, would improve glutamate metabolism, leading to further increased enzyme production. However, deletion of rocG dramatically decreased production of the alkaline cellulase Egl-237 in strain MGB874 (strain 874∆rocG).
Transcriptome analysis and cultivation profiles suggest that this phenomenon is attributable to impaired secretion of alkaline cellulase Egl-237 and nitrogen starvation, caused by decreased external pH and ammonium depletion, respectively. With NH3-pH auxostat fermentation, production of alkaline cellulase Egl-237 in strain 874∆rocG was increased, exceeding that in the wild-type-background strain 168∆rocG. Notably, in strain 874∆rocG, high enzyme productivity was observed throughout cultivation, possibly due to enhancement of metabolic flux from 2-oxoglutarate to glutamate and generation of metabolic energy through activation of the tricarboxylic acid (TCA) cycle. The level of alkaline cellulase Egl-237 obtained corresponded to about 5.5 g l-1, the highest level reported so far.
We found the highest levels of production of alkaline cellulase Egl-237 with the reduced-genome strain 874∆rocG and using the NH3-pH auxostat. Deletion of the glutamate dehydrogenase gene rocG enhanced enzyme production via a prolonged auxostat fermentation, possibly due to improved glutamate synthesis and enhanced generation of metabolism energy.
Bacillus subtilis; Protein secretion; Genome reduction; Glutamate metabolism
A mutant of Bacillus subtilis 6160 that had been isolated by its hyperproduction of alpha-amylase and protease lacked flagella and motility, and its content of autolytic enzyme(s) was reduced to one-third to one-fourth that of the parent. These phenotypic differences were completely co-transferred by the deoxyribonucleic acid (DNA) of the mutant when five DNA recipient strains of B. subtilis were transformed. The revertants, isolated by motility with a frequency of approximately 10(-7), recovered a normal level of autolytic activity and showed reduced productivity of alpha-amylase and protease. This point mutation allowed normal flagellin synthesis, spore formation, and rate of growth. The comparison of cell envelope of the mutant with that of the parent indicated that there was no significant difference except loss of flagella. Therefore the association at the cell surface of a group of extracellular proteins consisting of alpha-amylase, proteases, flagellin, and autolytic enzymes(s) seem to be coordinately regulated by the gene or seem to be affected coordinately by certain undetected alterations of the cell envelope.
Natural isolates of Bacillus subtilis exhibit a robust multicellular behavior known as swarming. A form of motility, swarming is characterized by a rapid, coordinated progression of a bacterial population across a surface. As a collective bacterial process, swarming is often associated with biofilm formation and has been linked to virulence factor expression in pathogenic bacteria. While the swarming phenotype has been well documented for Bacillus species, an understanding of the molecular mechanisms responsible remains largely isolated to gram-negative bacteria. To better understand how swarming is controlled in members of the genus Bacillus, we investigated the effect of a series of gene deletions on swarm motility. Our analysis revealed that a strain deficient for the production of surfactin and extracellular proteolytic activity did not swarm or form biofilm. While it is known that surfactin, a lipoprotein surfactant, functions in swarming motility by reducing surface tension, this is the first report demonstrating that general extracellular protease activity also has an important function. These results not only help to define the factors involved in eliciting swarm migration but support the idea that swarming and biofilm formation may have overlapping control mechanisms.
Many researchers have reported on the optimization of protease production; nevertheless, only a few have reported on the optimization of the production of organic solvent-tolerant proteases. Ironically, none has reported on thermostable organic solvent-tolerant protease to date. The aim of this study was to isolate the thermostable organic solvent-tolerant protease and identify the culture conditions which support its production. The bacteria of genus Bacillus are active producers of extra-cellular proteases, and the thermostability of enzyme production by Bacillus species has been well-studied by a number of researchers. In the present study, the Bacillus subtilis strain Rand was isolated from the contaminated soil found in Port Dickson, Malaysia.
A thermostable organic solvent-tolerant protease producer had been identified as Bacillus subtilis strain Rand, based on the 16S rRNA analysis conducted, as well as the morphological characteristics and biochemical properties. The production of the thermostable organic solvent-tolerant protease was optimized by varying various physical culture conditions. Inoculation with 5.0% (v/v) of (AB600 = 0.5) inoculum size, in a culture medium (pH 7.0) and incubated for 24 h at 37°C with 200 rpm shaking, was the best culture condition which resulted in the maximum growth and production of protease (444.7 U/ml; 4042.4 U/mg). The Rand protease was not only stable in the presence of organic solvents, but it also exhibited a higher activity than in the absence of organic solvent, except for pyridine which inhibited the protease activity. The enzyme retained 100, 99 and 80% of its initial activity, after the heat treatment for 30 min at 50, 55, and 60°C, respectively.
Strain Rand has been found to be able to secrete extra-cellular thermostable organic solvent-tolerant protease into the culture medium. The protease exhibited a remarkable stability towards temperature and organic solvent. This unique property makes it attractive and useful to be used in industrial applications.
Nagel, Charles W. (University of California, Davis) and Reese H. Vaughn. Comparison of growth and pectolytic enzyme production by Bacillus polymyxa. J. Bacteriol. 83:1–5. 1962.—Studies were made of pectolytic enzyme production by Bacillus polymyxa during growth. It was found that elaboration of enzyme occurred during logarithmic growth and ceased when the stationary phase was reached. The specific activity of the extra-cellular enzyme remained relatively constant until lysis occurred. The increased specific activity of the intracellular pectolytic enzyme may be explained if one assumes that the rate of secretion of the intracellular enzyme is dependent upon the concentration of the extracellular enzyme. The concentration of the intracellular pectolytic enzyme dropped markedly at the end of the logarithmic growth phase; the enzyme was released into the medium during the stationary growth phase and subsequent lysis of the cells. It was shown that the intra- and extracellular enzymes were similar or identical in that both were calcium-dependent pectic acid transeliminases.
Thermophilic Bacillus strains of phylogenetic Bacillus rRNA group 5 were described as a new genus Geobacillus. Their geographical distribution included oilfields, hay compost, hydrothermal vent or soils. The members from the genus Geobacillus have a growth temperatures ranging from 35 to 78°C and contained iso-branched saturated fatty acids (iso-15:0, iso-16:0 and iso-17:0) as the major fatty acids. The members of Geobacillus have similarity in their 16S rRNA gene sequences (96.5–99.2%). Thermophiles harboring intrinsically stable enzymes are suitable for industrial applications. The quest for intrinsically thermostable lipases from thermophiles is a prominent task due to the laborious processes via genetic modification.
Twenty-nine putative lipase producers were screened and isolated from palm oil mill effluent in Malaysia. Of these, isolate T1T was chosen for further study as relatively higher lipase activity was detected quantitatively. The crude T1 lipase showed high optimum temperature of 70°C and was also stable up to 60°C without significant loss of crude enzyme activity. Strain T1T was a Gram-positive, rod-shaped, endospore forming bacterium. On the basic of 16S rDNA analysis, strain T1T was shown to belong to the Bacillus rRNA group 5 related to Geobacillus thermoleovorans (DSM 5366T) and Geobacillus kaustophilus (DSM 7263T). Chemotaxonomic data of cellular fatty acids supported the affiliation of strain T1T to the genus Geobacillus. The results of physiological and biochemical tests, DNA/DNA hybridization, RiboPrint analysis, the length of lipase gene and protein pattern allowed genotypic and phenotypic differentiation of strain T1T from its validly published closest phylogenetic neighbors. Strain T1T therefore represents a novel species, for which the name Geobacillus zalihae sp. nov. is proposed, with the type strain T1T (=DSM 18318T; NBRC 101842T).
Strain T1T was able to secrete extracellular thermostable lipase into culture medium. The strain T1T was identified as Geobacillus zalihae T1T as it differs from its type strains Geobacillus kaustophilus (DSM 7263T) and Geobacillus thermoleovorans (DSM 5366T) on some physiological studies, cellular fatty acids composition, RiboPrint analysis, length of lipase gene and protein profile.
L-Malate repressed sporulation in the wild-type strain of Bacillus subtilis. When 75 mM L-malate was added to the growth medium at the time of inoculation, the appearance of heat-resistant spores was delayed 6 to 8 h. The synthesis of extracellular serine protease, alkaline phosphatase, glucose dehydrogenase, and dipicolinic acid was similarly delayed. Sporulation was not repressed when malate was added to the culture at t4 or later. A mutant was selected for ability to sporulate in the presence of malate. This strain could also sporulate in the presence of glucose. The malate-resistant mutant grew poorly with malate as sole carbon source, although it possessed an intact citric acid cycle, and it showed increased levels of malic enzyme. This indicates a defect in the metabolism of malate in the mutant. A mutant lacking malate dehydrogenase activity was also able to sporulate in the presence of malate. A model for the regulation of sporulation by malate is presented and discussed. Citric acid cycle intermediates other than malate did not affect sporulation. In contrast to previous results, sporulation of certain citric acid cycle mutants could be greatly increased or completely restored by the addition of intermediates after the enzymatic block. The results indicate that the failure of citric acid cycle mutants to sporulate can be adequately explained by lack of energy and lack of glutamate.
The genus Trichoderma includes species of great biotechnological value, both for their mycoparasitic activities and for their ability to produce extracellular hydrolytic enzymes. Although activity of extracellular laccase has previously been reported in Trichoderma spp., the possible number of isoenzymes is still unknown, as are the structural and functional characteristics of both the genes and the putative proteins. In this study, the system of laccases sensu stricto in the Trichoderma species, the genomes of which are publicly available, were analyzed using bioinformatic tools. The intron/exon structure of the genes and the identification of specific motifs in the sequence of amino acids of the proteins generated in silico allow for clear differentiation between extracellular and intracellular enzymes. Phylogenetic analysis suggests that the common ancestor of the genus possessed a functional gene for each one of these enzymes, which is a characteristic preserved in T. atroviride and T. virens. This analysis also reveals that T. harzianum and T. reesei only retained the intracellular activity, whereas T. asperellum added an extracellular isoenzyme acquired through horizontal gene transfer during the mycoparasitic process. The evolutionary analysis shows that in general, extracellular laccases are subjected to purifying selection, and intracellular laccases show neutral evolution. The data provided by the present study will enable the generation of experimental approximations to better understand the physiological role of laccases in the genus Trichoderma and to increase their biotechnological potential.
The neutral protease of Bacillus polymyxa had a broad pH optimum (6.0 to 7.2) for activity at 37 C. The enzyme was most stable at pH 5.6 to 5.8. The protease had an optimum temperature of 37 C and was quite thermostable up to 35 C, but at higher temperatures the stability decreased rapidly. The substrate specificity of the protease was similar to that of the neutral proteases of other members of the genus Bacillus. The enzyme was shown to be a zinc metalloprotease. However, manganous ions had a greater activating and stabilizing influence on the activity of this enzyme than zinc. Replacement of zinc in the native enzyme by manganese resulted in a 50% increase in activity. In addition, the prepared manganese metalloprotease had higher temperature and more alkaline pH optima than the native enzyme.