Number Of Carbon Sources Research Articles

Competitiveness of three biocontrol candidates against ochratoxigenic Penicillium nordicum under dry-cured meat environmental and nutritional conditions

The environmental conditions during the ripening of dry-cured meats and their nutritional composition promote the colonisation of their surface by Penicillium spp., including P. nordicum producer of ochratoxin A (OTA). The objective of this work was to study the competitiveness of three potential biocontrol candidates (Debaryomyces hansenii FHSCC 253H, Enterococcus faecium SE920 and Penicillium chrysogenum CECT, 20922) against the ochratoxigenic P. nordicum FHSCC4 under environmental and nutritional conditions simulating the ripening of dry-cured meat products. For this, the nutritional utilisation pattern, niche overlap index (NOI), interactions by dual-culture assays and OTA production were determined. The number of carbon sources (CSs) metabolised depended on the microorganism and the interacting water activity (aw) x temperature conditions. The number of CSs utilised by both filamentous fungi was quite similar and higher than those utilised by D. hansenii and E. faecium. The yeast isolate metabolised a number of CSs much larger than the bacterium. The NOI values showed that, in general, P. nordicum nutritionally dominated E. faecium and D. hansenii regardless of the environmental conditions evaluated. The relationship between the toxigenic and non-toxigenic fungal isolates depended on the aw x temperature combinations, although in none of the conditions a dominance of P. nordicum was observed. According to the interaction assays, both D. hansenii and P. chrysogenum decreased the growth of P. nordicum. The effect of D. hansenii could be attributed to the production of some extra-cellular compounds, while the action of P. chrysogenum is likely related to nutritional competition. In addition, both P. chrysogenum and D. hansenii reduced the OTA levels produced by P. nordicum. The effect of the yeast was more pronounced decreasing the concentration of OTA at quantities lower than the limit established by the Italian legislation. Therefore, P. chrysogenum and D. hansenii can be suggested as biocontrol candidates in the manufacture of dry-cured meat products.

Nutritional Studies on Production of Antibacterial Activity by the Zebra Mussel Antagonist, Pseudomonas fluorescens CL0145A

Pseudomonas fluorescens strain CL0145A was discovered at the New York State Museum Field Research Laboratory as an effective agent against the environmentally destructive zebra mussel, which has contaminated US waters. Dried cells of the microbe are being commercialized as an environmentally friendly solution to the problem. We found that antibiotic activity against the Gram-positive bacterium Bacillus subtilis is produced and excreted by this strain. We have carried out studies to optimize production of the antibiotic. Studies were begun in a complex corn meal medium. Activity was found in both cells and culture supernates and was maximal after one day of fermentation. Static fermentation conditions were found to be superior to shaken culture. Production of extracellular antibiotic in complex medium was found to be dependent on the content of sucrose and enzymehydrolyzed casein. Indeed, production was greater in sucrose plus enzyme-hydrolyzed casein than in the complex medium. Of a large number of carbon sources studied as improvements over sucrose, the best was glycerol. An examination of nitrogen sources showed that production was improved by replacement of enzymehydrolyzed casein with soy hydrolysates. Production in the simple glycerol-Hy-Soy medium was not improved by addition of an inorganic salt mixture or by complex nitrogen sources, with the exception of malt extract. In an attempt to keep the medium more defined, we studied the effect of amino acids and vitamins as replacements for malt extract. Of 21 amino acids and 7 vitamins, we found tryptophan, glutamine, biotin, and riboflavin to be stimulatory. The final medium contained glycerol, Hy- Soy, tryptophan, glutamine, biotin, and riboflavin.

Studies on biological reduction of chromate by Streptomyces griseus

Chromium is a toxic heavy metal used in various industries and leads to environmental pollution due to improper handling. The most toxic form of chromium Cr(VI) can be converted to less toxic Cr(III) by reduction. Among the actinomycetes tested for chromate reduction, thirteen strains reduced Cr(VI) to Cr(III), of which one strain of Streptomyces griseus (NCIM 2020) was most efficient showing complete reduction within 24 h. The organism was able to use a number of carbon sources as electron donors. Sulphate, nitrate, chloride and carbonate had no effect on chromate reduction during growth while cations such as Cd, Ni, Co and Cu were inhibitory to varying degrees. Chromate reduction was associated with the bacterial cells and sonication was the best method of cell breakage to release the enzyme. The enzyme was constitutive and did not require presence of chromate during growth for expression of activity. Chromate reduction with cell free extract (CFE) was observed without added NADH. However, addition of NAD(P)H resulted in 2–3-fold increase in activity. Chromate reductase showed optimum activity at 28 °C and pH 7.

Role of Acinetobacter baylyi Crc in Catabolite Repression of Enzymes for Aromatic Compound Catabolism

Here, we describe for the first time the Crc (catabolite repression control) protein from the soil bacterium Acinetobacter baylyi. Expression of A. baylyi crc varied according to the growth conditions. A strain with a disrupted crc gene showed the same growth as the wild type on a number of carbon sources. Carbon catabolite repression by acetate and succinate of protocatechuate 3,4-dioxygenase, the key enzyme of protocatechuate breakdown, was strongly reduced in the crc strain, whereas in the wild-type strain it underwent strong catabolite repression. This strong effect was not based on transcriptional regulation because the transcription pattern of the pca-qui operon (encoding protocatechuate 3,4-dioxygenase) did not reflect the derepression in the absence of Crc. pca-qui transcript abundance was slightly increased in the crc strain. Lack of Crc dramatically increased the mRNA stability of the pca-qui transcript (up to 14-fold), whereas two other transcripts (pobA and catA) remained unaffected. p-Hydroxybenzoate hydroxylase activity, encoded by pobA, was not significantly different in the absence of Crc, as protocatechuate 3,4-dioxygenase was. It is proposed that A. baylyi Crc is involved in the determination of the transcript stability of the pca-qui operon and thereby effects catabolite repression.

Effect of Microbial Species Richness on Community Stability and Community Function in a Model Plant-Based Wastewater Processing System

Microorganisms will be an integral part of biologically based waste processing systems used for water purification or nutrient recycling on long-term space missions planned by the National Aeronautics and Space Administration. In this study, the function and stability of microbial inocula of different diversities were evaluated after inoculation into plant-based waste processing systems. The microbial inocula were from a constructed community of plant rhizosphere-associated bacteria and a complexity gradient of communities derived from industrial wastewater treatment plant-activated sludge. Community stability and community function were defined as the ability of the community to resist invasion by a competitor (Pseudomonas fluorescens 5RL) and the ability to degrade surfactant, respectively. Carbon source utilization was evaluated by measuring surfactant degradation and through Biolog and BD oxygen biosensor community level physiological profiling. Community profiles were obtained from a 16S-23S rDNA intergenic spacer region array. A wastewater treatment plant-derived community with the greatest species richness was the least susceptible to invasion and was able to degrade surfactant to a greater extent than the other complexity gradient communities. All communities resisted invasion by a competitor to a greater extent than the plant rhizosphere isolate constructed community. However, the constructed community degraded surfactant to a greater extent than any of the other communities and utilized the same number of carbon sources as many of the other communities. These results demonstrate that community function (carbon source utilization) and community stability (resistance to invasion) are a function of the structural composition of the community irrespective of species richness or functional richness.

Uso de diferentes fontes de carbono por estirpes de Gluconacetobacter diazotrophicus isoladas de cana-de-açúcar

O objetivo deste trabalho foi quantificar a população de Gluconactobacter diazotrophicus presente em plântulas de 34 variedades de cana-de-açúcar, e caracterizar os isolados quanto à capacidade de utilizar diversas fontes de carbono e formar pigmento róseo em presença de luz. A população de G. diazotrophicus foi quantificada pela técnica do número mais provável e isolada em meios de cultura semi-seletivos. A população de G. diazotrophicus foi maior no sistema radicular do que na parte aérea, e maior nas variedades brasileiras de cana-de-açúcar. Os isolados utilizaram poucas fontes de carbono, e aqueles obtidos do sistema radicular utilizaram maior número de fontes, em comparação aos da parte aérea. Apenas a estirpe padrão Ppe-4 e quatro outros isolados formam pigmento róseo em presença de luz. A baixa variação observada pode estar relacionada com o habitat ou com a adaptação dessa população às condições específicas do interior das plantas e, por isso, a estrutura genética da população dessas bactérias é limitada e conservada.

Guanosine 3′,5′-bispyrophosphate coordinates global gene expression during glucose-lactose diauxie in Escherichia coli

Guanosine 3',5'-bispyrophosphate (ppGpp), also known as "magic spot," has been shown to bind prokaryotic RNA polymerase to down-regulate ribosome production and increase transcription of amino acid biosynthesis genes during the stringent response to amino acid starvation. Because many environmental growth perturbations cause ppGpp to accumulate, we hypothesize ppGpp to have an overarching role in regulating the genetic program that coordinates transitions between logarithmic growth (feast) and growth arrest (famine). We used the classic glucose-lactose diauxie as an experimental system to investigate the temporal changes in transcription that accompany growth arrest and recovery in wild-type Escherichia coli and in mutants that lack RelA (ppGpp synthetase) and other global regulators, i.e., RpoS and Crp. In particular, diauxie was delayed in the relA mutant and was accompanied by a 15% decrease in the number of carbon sources used and a 3-fold overall decrease in the induction of RpoS and Crp regulon genes. Thus the data significantly expand the previously known role of ppGpp and support a model wherein the ppGpp-dependent redistribution of RNA polymerase across the genome is the driving force behind control of the stringent response, general stress response, and starvation-induced carbon scavenging. Our conceptual model of diauxie describes these global control circuits as dynamic, interconnected, and dependent upon ppGpp for the efficient temporal coordination of gene expression that programs the cell for transitions between feast and famine.

Rhizobacterial community-level, sole carbon source utilization pattern affects the delay in the bacterial wilt of tomato grown in rhizobacterial community model system

Characterizing rhizomicrobial community structure is important to our understanding of the mechanisms of suppressive soils towards soilborne plant diseases. We investigated whether the bacterial community structure, i.e., the number of the constituent bacterial strains and the community-level, sole carbon source utilization pattern of rhizobacteria estimated by BIOLOG EcoPlates, affects bacterial wilt of tomato. To assess their impact on the bacterial wilt, we used 15 artificial soil systems into which 5–20 rhizobacterial isolates from a disease-suppressive soil were inoculated. Although most of the tomato plants wilted by 16 days after pathogen inoculation, significant negative relationships were observed between the number of wilted plants, the number of the bacterial strains and the number of carbon sources that the rhizobacterial community was able to utilize. BIOLOGs showed that several carbon sources were utilized by the pathogen but not by the rhizobacterial community from the fastest-wilting treatments, suggesting that competition between the pathogen and the other rhizobacteria for carbon sources played an important role in suppressing the growth of the pathogen.

β-Methyl-xyloside: positive effect on xylanase induction in Cellulomonas flavigena

Synthesis of extracellular xylanase in Cellulomonas flavigena is induced in the presence of xylan and sugarcane bagasse as substrates. The essential factors for efficient production of xylanase are the appropriate medium composition and an inducing substrate. The increase in xylanase production levels in C. flavigena were tested with a number of carbon sources and different culture conditions. Xylose, arabinose, glycerol and glucose did not induce xylanase production in this microorganism. beta-Methyl-xyloside (beta-mx), a structural analog of xylobiose, also did not induce xylanase when used as the sole carbon source, but when xylan or sugar cane bagasse was supplemented with beta-mx, extracellular xylanase production increased by 25 or 46%, respectively. The response of C. flavigena to xylan plus beta-mx was accompanied by a significant accumulation of reducing sugar, an effect not observed with the combination sugarcane bagasse plus beta-mx as substrate. To our knowledge, this is the first report on the effect of beta-mx on the induction of xylanase in C. flavigena.

A simple imaging method for biomass determination

An inexpensive and fast method based on images taken during growth of bacterial cells on multi-well plates was developed for biomass quantification. A correlation of 85% between the results obtained by image analysis and optical density measurements was obtained. This simple method allows the assessment of growth with highly aggregated cell cultures and the rapid screening of a large number of carbon sources.

Comparative growth studies of the extreme thermophile Sulfolobus acidocaldarius in submerged and solidified substrate cultures

An attempt was made, for the first time, to exploit cultures on solidified substrates (SSC) as an alternative to submerged cultures (SmC) for growing extremophilic micro-organisms. The extreme thermophilic archaebacterium Sulfolobus acidocaldarius was grown on a number of carbon sources and, in all experiments, biomass yields and growth rates were always higher in SSC than in the corresponding SmC. Inoculum age significantly affected growth characteristics on both types of fermentation. Heavy growth of the micro-organism in SSC was observed on low-cost carbon sources such as starch. Wheat bran significantly enhanced growth characteristics when used to supplement starch media. The results of this work show that cultures on solid surfaces could be a promising alternative method for growing extreme thermophiles.

Genetic Recombination in Lactobacilli

ABSTRACTAn interspecies genetic recombination by fusion of protoplasts of antibiotic-resistant clones of lactobacilli: Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus helveticus, Lactobacillus casei, and Lactobacillus plantarum has been accomplished. It has been shown that the conditions of degradation of the lactobacilli cell wall allow a high relative share of formed protoplasts to be achieved. After the protoplast fusion and regeneration of the cell wall a heterogenic population is obtained. A series of recombinant clones has been selected, which differ from the parent cultures in improved or new qualities, such as higher reproducibility, acid-forming ability, assimilation and fermentation of a greater number of carbon sources, phage-resistance etc. Among them have been selected the recombinant strains—Lactobacillus LAB 8, Lactobacillus LHC 28, Lactobacillus LBC 7, Lactobacillus LBC 16, Lactobacillus LPC 12, Lactobacillus LPC 48, Lactobacillus LPC 51.

The Significance of Long-Chain Fatty Acid Composition and Other Phenotypic Characteristics in Determining Relationships Among Some Candida, Kluyveromyces and Saccharomyces Species

Summary Thirty one species representing the genera Candida, Kluyveromyces and Saccharomyces were grouped according to their cellular long-chain fatty acid compositions, carbon source utilization patterns and degree of cell differentiation. The coordinate use of these different phenotypic characteristics provided a convenient method to establish possible teleomorph and anamorph relations as well as similarities among yeasts. Yeasts with known teleomorph-anamorph relations were generally closely grouped while unrelated yeasts were positioned some distances from each other. An interesting correlation was also found between the different phenotypic characteristics of the species studied. The presence of linolenic acid correlated with the formation of pseudomycelium and/or true hyphae as well as the utilzation of a large number of carbon sources while the absence of linolenic acid correlated with the formation of rudimentary pseudomycelium and/or single cells and the utilization of only a few carbon sources.

Ammonium Ion Repression of Sporulation in Saccharomyces cerevisiae

The role of NH+ 4 in the regulation of sporulation in Saccharomyces cerevisiae has been studied by analysing the effects of NH+ 4 and methylammonium ions on sporulation in a wild-type strain; a strain homozygous for the spd1 mutation, (derepressed sporulation on a number of carbon sources, reduced sensitivity to NH+ 4-inhibition of sporulation); and a strain homozygous for the gdhA6 mutation, (the structural gene for the anabolic NADP+-dependent glutamate dehydrogenase). The addition of ammonium or methylammonium ions to sporulation medium resulted in incomplete ascus formation. The gdhA6 mutation resulted in a loss of sensitivity to NH+ 4-inhibition of initiation of sporulation. At higher concentrations of NH+ 4 the strain homozygous for the gdhA6 mutation was even less sensitive than the sporulation-derepressed strain. However, in the formation of complete asci all three strains behaved very similarly over the whole range of ammonium sulphate concentration. These studies indicate there are at least two separate stages affected by NH+ 4; one early, possibly initiation, the other later, concerned with the organization and delimitation of mature spores. From the reduced sensitivity to NH+ 4-inhibition of initiation of sporulation conferred by the gdhA6 mutation, and the fact that similar results were obtained using methylammonium ion, it is concluded that some metabolite of NH+ 4 is responsible rather than NH+ 4 itself. In addition, the data provide some insight into the nature of the spdl mutation.

Regulation of Extracellular Alkaline Protease Activity by Histidine in a Collagenolytic Vibrio alginolyticus Strain

Vibrio alginolyticus synthesized an inducible extracellular collagenase in a peptone medium during the stationary growth phase. These cultures also possessed extracellular alkaline serine protease activity. The alkaline protease activity did not require a specific inducer and it was produced in tryptone or minimal media. The collagenase was not produced in either the tryptone or minimal media. The alkaline protease activity was sensitive to catabolite repression by a number of carbon sources, including glucose, and by amino acids and ammonium ions. Cyclic AMP, dibutyryl cyclic AMP and cyclic GMP did not relieve catabolite repression. Histidine and urocanic acid stimulated the production of alkaline protease activity in tryptone and minimal media. Other compounds associated with the histidine utilization (hut) pathway did not increase alkaline protease activity. Histidine reversed the repression of alkaline protease activity by glucose of (NH4)2SO4 in minimal medium. Histidine and the compounds associated with the hut pathway inhibited collagenase production.

Regulation of Extracellular Collagenase Production in Achromobacter iophagus

SUMMARY: Achromobacter iophagus synthesized extracellular collagenase in a highly aerated peptone medium at the late-exponential and early-stationary phases of growth. Collagenase synthesis was subject to end-product repression and was repressed by various amino acids and ammonium ions. Glutamine caused severe repression of collagenase production. Collagenase synthesis was sensitive to catabolite repression by glucose and a number of carbon sources. Cyclic AMP, dibutyryl cyclic AMP and cyclic GMP did not relieve catabolite repression. Glucose and 2-deoxyglucose caused a severe transient repression. Although rifampicin and chloramphenicol immediately inhibited RNA and protein synthesis, respectively, they failed to inhibit collagenase production completely. No intracellular preformed collagenase was detected and collagenase production ceased when induced cells were washed and resuspended in buffer.

Factors affecting sporulation by Phomopsis phaeolorum

Light and nutrition are the important factors in the production of pycnidia and conidia by cowpea isolates of the Phomopsis state of Diaporthe phaseolorum. The highest number of pycnidia and conidia were produced on plant tissue exposed to cool-white fluorescent light. In semisynthetic media more pycnidia were formed at high glucose concentrations, but they matured more slowly than those formed at lower glucose concentrations. Both the level of conidiation and the percentage of pycnidia that formed conidia were higher at lower glucose concentrations. The best artificial medium for inducing a high number of pycnidia containing abundant conidia was one that contained 0.4% glucose and 0.4% NaNO3. A number of carbon sources could replace glucose in this medium.

Inhibitory effect of Trichoderma viride Pers. ex Fr. filtrates on Fomes annosus (Fr.) Cke. In relation to some carbon sources

The mycelial yield of Trichoderma viride on a number of carbon sources and the inhibitory effect of its filtrates on Fomes annosus were investigated. d-Xylose and d-glucose as carbon sources in the media gave the highest degree of inhibition when their filtrates were directly tested against F. annosus mycelium. The protection of pine wood blocks with filtrates was most effective when these were derived from cellulose and d-xylose.

Factors Affecting the Sexual Reproduction of a Dermatophyte, Arthroderma benhamiae, in Synthetic Media

AbstractSexual reproduction of many dermatophytes is easily induced in complex media such as soil plus keratin. In Arthroderma benhamiae this process could be initiated also in synthetic agar media. A number of carbon sources (glucose, fructose, galactose, mannose, maltose, lactose, sorbose, sucrose) had about the same stimulatory effect on reproduction, while xylose was inhibitory. Organic sulphur was not crucial for the process in contrast to the nitrogen supply. The nitrogen sources could be divided into four groups; I. very stimulatory (arginine, citrulline, isoleucine, leucine, ornithine, phenylalanine, proline, valine, glutathione); II. stimulatory (alanine, asparagine, lysine, serine); III. slightly stimulatory (aspartic acid, cysteine, glutamic acid, glycine, histidine, urea, NH4Cl, NH4‐tartrate); IV. inhibitory (hydroxyproline, methionine, threonine, tryptophan). Synergistic effects were shown between some amino acids. Generally a combination between 5 g/l glucose and 300–400 mg/l nitrogen induced the largest number of cleistothecia, regardless of the nitrogen source used. The level varied between the sources, however. A C/N ratio of about 10 was optimal while a value above 20 gave no cleistothecia. The optimal temperature for the process was 30°C. Sexual reproduction occurred between pH 4.4 and 8.0 (final values). However, at a final pH above 7.2 the number of ascospores/cleistothecium was reduced.

Influence of some carbon sources on growth of Cochliobolus sativus

Four isolates of C. sativus were able to use a number of carbon sources to varying degrees with little evidence of a differential growth response by the isolates. With most carbon sources the response was different when growth on liquid media was compared with that on agar media. Dextrin and L-sorbose were exceptions as dextrin supported good growth with both types and L-sorbose poor with both. Lactose supported the best mycelial growth on liquid media and dextrin the best radial growth and sporulation on agar media when compared with sucrose.