Accumulation of intracellular inorganic sulfate by Penicillium chrysogenum

Sulfur regulation of the sulfate transporter genes sutA and sutB in Penicillium chrysogenum

Penicillium chrysogenum uses sulfate as a source of sulfur for the biosynthesis of penicillin. Sulfate uptake and the mRNA levels of the sulfate transporter-encoding sutB and sutA genes are all reduced by high sulfate concentrations and are elevated by sulfate starvation. In a high-penicillin-yielding strain, sutB is effectively transcribed even in the presence of excess sulfate. This deregulation may facilitate the efficient incorporation of sulfur into cysteine and penicillin.

Sulfate transport in Penicillium chrysogenum: cloning and characterization of the sutA and sutB genes

In industrial fermentations, Penicillium chrysogenum uses sulfate as the source of sulfur for the biosynthesis of penicillin. By a PCR-based approach, two genes, sutA and sutB, whose encoded products belong to the SulP superfamily of sulfate permeases were isolated. Transformation of a sulfate uptake-negative sB3 mutant of Aspergillus nidulans with the sutB gene completely restored sulfate uptake activity. The sutA gene did not complement the A. nidulans sB3 mutation, even when expressed under control of the sutB promoter. Expression of both sutA and sutB in P. chrysogenum is induced by growth under sulfur starvation conditions. However, sutA is expressed to a much lower level than is sutB. Disruption of sutB resulted in a loss of sulfate uptake ability. Overall, the results show that SutB is the major sulfate permease involved in sulfate uptake by P. chrysogenum.

Sulfate transport in Penicillium chrysogenum plasma membranes

Transport studies with Penicillium chrysogenum plasma membranes fused with cytochrome c oxidase liposomes demonstrate that sulfate uptake is driven by the transmembrane pH gradient and not by the transmembrane electrical potential. Ca2+ and other divalent cations are not required. It is concluded that the sulfate transport system catalyzes the symport of two protons with one sulfate anion.

Isolation and characterisation of genes for sulphate activation and reduction in Aspergillus nidulans: implications for evolution of an allosteric control region by gene duplication

A region of the Aspergillus nidulans genome carrying the sA and sC genes, encoding PAPS reductase and ATP sulphurylase, respectively, was isolated by transformation of an sA mutant with a cosmid library. The genes were subcloned and their functions confirmed by retransformation and complementation of A. nidulans strains carrying sA and sC mutations. The physical distance of 2 kb between the genes corresponds to a genetic distance of 1 cM. While the deduced amino acid sequence of the sA gene product shows homology with the equivalent MET16 gene product of Saccharomyces cerevisiae, the sC gene product resembles the equivalent MET3 yeast gene product at the N-terminal end, but differs markedly from it at the C-terminal end, showing homology to the APS kinases of several microorganisms. It is proposed that this C-terminal region does not encode a functional APS kinase, but is responsible for allosteric regulation by PAPS of the sulphate assimilation pathway in A. nidulans, and that the ATP sulphurylase encoding-gene (sC) of filamentous ascomycetes may have evolved from a bifunctional gene similar to the nodQ gene of Rhizobium meliloti.

Reverse transsulfuration and its relationship to thienamycin biosynthesis in Streptomyces cattleya

Cystathionine gamma-lyase (EC 4.4.1.1) was purified from Streptomyces cattleya, an actinomycete which produces the unusual beta-lactam antibiotic thienamycin. The enzyme displays broad substrate specificity and is similar to gamma-lyases purified from other microorganisms. That the gamma-lyase functions in vivo to provide cysteine for antibiotic synthesis was shown by two types of experiments. First, cystathionine and methionine, as well as cysteine itself, are efficiently utilized by S. cattleya for thienamycin biosynthesis. Second, propargylglycine, a mechanism-based inactivator of cystathionine gamma-lyase in vitro, inhibits the synthesis of thienamycin in vivo. This inhibition can be substantially reversed by providing the cells with another source of cysteine, such as cystine.

Isolation of sulphate transport defective mutants of Candida utilis: further evidence for a common transport system for sulphate, sulphite and thiosulphate

Selenate-resistant mutants of Candida utilis were isolated. They did not take up sulphate while incorporation of an organic sulphur source, such as L-methionine, was similar to the wild-type strain. They grew poorly on sulphate, sulphite and thiosulphate and, as expected, grew well on methionine. Sulphite reductase activities of the mutants were similar to the wild type strain. The properties of these mutants support the view of a common transport system for sulphate, sulphite and thiosulphate.

Sulphate transport in Candida utilis

Sulphate uptake by Candida utilis follows Michaelis-Menten type kinetics characterized by a Km of 1.43 mM for sulphate. The process is unidirectional, pH, temperature and energy dependent. Molybdate, selenate, thiosulphate, chromate and sulphite are competitive inhibitors. Dithionite is a mixed-type inhibitor of sulphate uptake. If cells are pre-incubated with sulphate, sulphite, thiosulphate, dithionite or sulphide, sulphate uptake is severely blocked. Inhibition by endogenous sulphate, sulphite and thiosulphate was specific for sulphate uptake. Thus, incorporation of extracellular sulphate seems to be under the control of a heterogeneous pool of sulphur compounds. These results are discussed in connection with the regulation of sulphur amino acid biosynthesis in C. utilis.

Assimilatory sulfur metabolism in marine microorganisms: characteristics and regulation of sulfate transport in Pseudomonas halodurans and Alteromonas luteo-violaceus

Sulfate transport capacity was not regulated by cysteine, methionine, or glutathione in Pseudomonas halodurans, but growth on sulfate or thiosulfate suppressed transport. Subsequent sulfur starvation of cultures grown on all sulfur sources except glutathione stimulated uptake. Only methionine failed to regulate sulfate transport in Alteromonas luteo-violaceus, and sulfur starvation of all cultures enhanced transport capacity. During sulfur starvation of sulfate-grown cultures of both bacteria, the increase in transport capacity was mirrored by a decrease in the low-molecular-weight organic sulfur pool. Little metabolism of endogenous inorganic sulfate occurred. Cysteine was probably the major regulatory compound in A. luteo-violaceus, but an intermediate in sulfate reduction, between sulfate and cysteine, controlled sulfate transport in P. halodurans. Kinetic characteristics of sulfate transport in the marine bacteria were similar to those of previously reported nonmarine systems in spite of significant regulatory differences. Sulfate and thiosulfate uptake in P. halodurans responded identically to inhibitors, were coordinately regulated by growth on various sulfur compounds and sulfur starvation, and were mutually competitive inhibitors of transport, suggesting that they were transported by the same mechanism. The affinity of P. halodurans for thiosulfate was much greater than for sulfate.

[Possibilities for direct manipulation of gene expression of microbial secondary metabolism]

The present review deals with some theoretical and applied aspects of directed manipulations of control mechanisms governing the expression of microbial secondary metabolism. In attempting to make broad generalizations, the production of secondary metabolites is discussed in terms of the cellular differentiation of relevant organisms. On the basis of the actual information about the regulation of microbial idiolite synthesis, some potential ways for the quantitative and the qualitative improvement of secondary metabolite production are discussed. A number of examples demonstrate the effectiveness of rational strategies of strain development, e. g., the removal of non-specific repressions of secondary metabolism by environmental factors, the excessive production of precursors due to altered control of intermediary metabolism, the increased resistance of producer organism against the autotoxicity of some idiolites, the deletion of alternative pathways of the primary and secondary metabolism, manipulations concerning the product spectrum, the deletion of feedback mechanisms, and elimination of degradating pathways in the secondary metabolism etc. The scope and limitations of rational strategies of strain improvement by genetic and physiologic manipulations are subjected to final discussion.

Sulfate transport in cultured tobacco cells

Sulfate transport by tobacco (Nicotiana tabacum L. var. Xanthi) cells cultured on either l-cysteine or sulfate as a sole sulfur source was measured. The transport rate on either sulfur source was low during pre-exponential growth, increased during exponential growth, and was maximal in late exponential cells. The initial increase in transport rate was correlated with a decline in the intracellular sulfate, but was not correlated with the amino acid content of the cells which remained relatively constant before the depletion of the endogenous sulfate pool. The previously reported inhibition of sulfate transport by l-cysteine was shown to be caused by an elevation in intracellular sulfate resulting from the degradation of cysteine to sulfate. It is proposed that the intracellular sulfate pool is the major factor regulating the entry of sulfate into tobacco cells.

Synthesis of cephalosporin C from sulfate by mutants of Cephalosporium acremonium

The innate ability of Cephalosporium acremonium to use methionine preferentially over sulfate for synthesis of cephalosporin C can be influenced through mutation. Mutants of C. acremonium with altered capacity to utilize sulfate for synthesis of antibiotic were isolated and partially characterized with respect to the uptake of sulfate and the regulation of arylsulfatase.

Regulation of sulfate transport in filamentous fungi

Inorganic sulfate enters the mycelia of Aspergillus nidulans, Penicillium chrysogenum, and Penicillium notatum by a temperature-, energy-, pH-, ionic strength-, and concentration-dependent transport system ("permease"). Transport is unidirectional. In the presence of excess external sulfate, ATP sulfurylase-negative mutants will accumulate inorganic sulfate intracellularly to a level of about 0.04 m. The intracellular sulfate can be retained against a concentration gradient. Retention is not energy-dependent, nor is there any exchange between intracellular (accumulated) and extracellular sulfate. The sulfate permease is under metabolic control. Sulfur starvation of high methionine-grown mycelia results in about a 1000-fold increase in the specific sulfate transport activity at low external sulfate concentrations. l-Methionine is a metabolic repressor of the sulfate permease, while intracellular sulfate and possibly l-cysteine (or a derivative of l-cysteine) are feedback inhibitors. Sulfate transport follows hyperbolic saturation kinetics with a Michaelis constant (Km) value of 6 x 10(-5) to 10(-4)m and a V(max) (for maximally sulfurstarved mycelia) of about 5 micromoles per gram per minute. Refeeding sulfur-starved mycelia with sulfate or cysteine results in about a 10-fold decrease in the V(max) value with no marked change in the Km. Azide and dinitrophenol also reduce the V(max.).

Specificity and control of choline-O-sulfate transport in filamentous fungi

Choline-O-sulfate uptake by Penicillium notatum showed the following characteristics. (i) Transport was mediated by a permease which is highly specific for choline-O-sulfate. No significant inhibition of transport was caused by choline, choline-O-phosphate, acetylcholine, ethanolamine-O-phosphate, ethanolamine-O-sulfate, methanesulfonyl choline, 2-aminoethane thiosulfate, or the monomethyl or dimethyl analogues of choline-O-sulfate. Similarly, no significant inhibition was caused by any common sulfur amino acid or inorganic sulfur compound. Mutants lacking the inorganic sulfate permease possessed the choline-O-sulfate permease at wild-type levels. (ii) Choline-O-sulfate transport obeyed saturation kinetics (K(m) = 10(-4) to 3 x 10(-4)m; V(max) = 1 to 6 mumoles per g per min). The kinetics of transport between 10(-9) and 10(-1)m external choline-O-sulfate showed that only one saturable mechanism is present. (iii) Transport was sensitive to 2,4-dinitrophenol, azide, N-ethylmaleimide, p-chloromercuribenzoate, and cyanide. Ouabain, phloridzin, and eserine had no effect. (iv) Transport was pH-dependent with an optimum at pH 6. Variations in the ionic strength of the incubation medium had no effect. (v) Transport was temperature-dependent with a Q(10) of greater than 2 between 3 and 40 C. Transport decreased rapidly above 40 C. (vi) Ethylenediaminetetraacetate (sodium salts, pH 6) had no effect, nor was there any stimulation by metal or nonmetal ions. Cu(++), Ag(+), and Hg(++) were inhibitory. (vii) The initial rate at which the ester is transported was independent of intracellular hydrolysis. After long periods of incubation (> 10 min), a significant proportion of the transported choline-O-sulfate was hydrolyzed intracellulary. In the presence of 5 x 10(-3)m external choline-O-sulfate, the mycelia accumulated choline-O-sulfate to an apparent intracellular concentration of 0.075 m by 3 hr. Transport was unidirectional. No efflux or exchange of (35)S-choline-O-sulfate was observed when preloaded mycelia were suspended in buffer alone or in buffer containing a large excess of unlabeled choline-O-sulfate. (viii) The specific transport activity of the mycelium depended on the sulfur source used for growth. (ix) Sulfur starvation of sulfur-sufficient mycelium resulted in an increase in the specific transport activity of the mycelium. This increase was prevented by cycloheximide, occurred only when a metabolizable carbon source was present, and resulted from an increase in the V(max) of the permease, rather than from a decrease in K(m). The increase could be partially reversed by refeeding the mycelia with unlabeled choline-O-sulfate, sulfide, sulfite, l-homocysteine, l-cysteine, or compounds easily converted to cysteine. The results strongly suggested that the choline-O-sulfate permease is regulated primarily by repression-derepression, but that intracellular choline-O-sulfate and cysteine can act as feedback inhibitors.

Role of methionine in cephalosporin synthesis

Methionine has an almost unique stimulatory effect on biosynthesis of cephalosporins (by Cephalosporium acremonium). No other sulfur-containing compound tested, except dl-methionine-dl-sulfoxide, replaced methionine. dl-Methionine stimulated the synthesis of cephalosporins when added after the growth phase. The utilization of inorganic sulfate was repressed by methionine. Experiments with l-methionine-S(35) showed that essentially all the sulfur in the cephalosporins was derived from methionine. Sulfur-labeled compounds found in the soluble pool from cells grown with methionine-S(35) were methionine, homocysteine, taurine, cystathionine, cysteic acid, glutathionine, and cysteine. dl-Serine-3-C(14) was incorporated into the antibiotics, and its utilization was stimulated by methionine. l-Cysteine had a sparing effect on the incorporation of methionine-S(35) and serine-C(14) into the antibiotics. The data are consistent with the hypothesis that a cystathionine-mediated pathway is operative in the transfer of sulfur between methionine and cysteine.