Presence Of Various Carbon Sources Research Articles

Comparative Genomic Analysis of a Methylorubrum rhodesianum MB200 Isolated from Biogas Digesters Provided New Insights into the Carbon Metabolism of Methylotrophic Bacteria.

Methylotrophic bacteria are widely distributed in nature and can be applied in bioconversion because of their ability to use one-carbon source. The aim of this study was to investigate the mechanism underlying utilization of high methanol content and other carbon sources by Methylorubrum rhodesianum strain MB200 via comparative genomics and analysis of carbon metabolism pathway. The genomic analysis revealed that the strain MB200 had a genome size of 5.7 Mb and two plasmids. Its genome was presented and compared with that of the 25 fully sequenced strains of Methylobacterium genus. Comparative genomics revealed that the Methylorubrum strains had closer collinearity, more shared orthogroups, and more conservative MDH cluster. The transcriptome analysis of the strain MB200 in the presence of various carbon sources revealed that a battery of genes was involved in the methanol metabolism. These genes are involved in the following functions: carbon fixation, electron transfer chain, ATP energy release, and resistance to oxidation. Particularly, the central carbon metabolism pathway of the strain MB200 was reconstructed to reflect the possible reality of the carbon metabolism, including ethanol metabolism. Partial propionate metabolism involved in ethyl malonyl-CoA (EMC) pathway might help to relieve the restriction of the serine cycle. In addition, the glycine cleavage system (GCS) was observed to participate in the central carbon metabolism pathway. The study revealed the coordination of several metabolic pathways, where various carbon sources could induce associated metabolic pathways. To the best of our knowledge, this is the first study providing a more comprehensive understanding of the central carbon metabolism in Methylorubrum. This study provided a reference for potential synthetic and industrial applications of this genus and its use as chassis cells.

Contribution of the capsular polysaccharide layer to antibiotic resistance in bifidobacteria.

Bifidobacteria have been shown to produce exopolysaccharides (EPS), which are polymeric structures composed of various carbohydrates, commonly containing glucose, galactose, and rhamnose. EPS are produced by different bifidobacterial taxa commonly identified in the human gut, such as Bifidobacterium breve and Bifidobacterium longum subsp. longum, and have been suggested to modulate the interaction of bifidobacterial cells with other members of the human gut microbiota as well as with their host. In this study, we evaluated if bifidobacterial EPS production of four selected EPS-producing strains is associated with enhanced resistance to antibiotic treatments through MIC analysis when compared to bacterial cultures that do not produce exopolysaccharides. Our results showed that an increase in EPS production by modifying the growth medium with different carbon sources, i.e. glucose, galactose or lactose and/or by applying stressful conditions, such as bile salts and acidity, is associated with a tolerance enhancement of bifidobacterial cells toward various beta-lactam antibiotics. In addition, after analyzing the production of EPS at the phenotypic level, we explored the genes involved in the production of these structures and evaluated their expression, in presence of various carbon sources, using RNAseq. Overall, this study provides preliminary experimental evidence showing how bifidobacterial EPS modifies the level of susceptibility of these bacteria towards antibiotics.

The Effect of Atranes on the Growth of <i>Rhodococcus qingshengii</i> VKM Ac-2784D in the Presence of Various Carbon Sources and on Its Ability to Degrade Naphthalene

Abstract—Rhodococcus qingshengii VKM Ac-2784D isolated from the rhizosphere of Elytrigia repens, is a promising oil degrader. To increase its biotechnological potential, the effect of atranes (potential growth stimulants) on its growth and naphthalene degradation was studied. The effect of the studied atranes on R. qingshengii VKM Ac-2784D was shown to depend on the nature of the carbon source: addition of atranes had practically no effect on the growth rate of bacteria in the rich BTN medium; in the media 8E and 8E with glucose, it baused short-term activation of growth, characterized by a shorter lag phase. In the presence of naphthalene, atranes had a predominantly negative effect on the growth of R. qingshengii VKM Ac-2784D. The studied atranes had a negative effect on the rate of naphthalene decomposition by R. qingshengii VKM Ac-2784D, and also decreased the cell wall hydrophobicity and the synthesis of extracellular biosurfactants. It may therefore be assumed that the studied compounds will have a negative effect on the rate of naphthalene decomposition by this microorganism.

The Effect of Atranes on the Growth of Rhodococcus qingshengii VKM Ac-2784D in the Presence of Various Carbon Sources and on Its Ability to Degrade Naphthalene

The Effect of Atranes on the Growth of Rhodococcus qingshengii VKM Ac-2784D in the Presence of Various Carbon Sources and on Its Ability to Degrade Naphthalene

Identification and Characterisation of the Salt Tolerant Phosphate-Solubilising Bacterial Isolates for Enhancing Soil Fertility

In this study, 13 bacteria were isolated from the agricultural soils of Kyaukse city, Myanmar, and out of these isolates, two bacteria isolates viz. JU-24 and JU-33 are found to be potent phosphate (P) solubilisers and are selected for further studies. These two isolates are identified as Bacillus megaterium based on the 16S rRNA gene sequence. When the growth rates of these two isolates were tested for salt tolerance, they could grow well in media with NaCl concentrations of 3%, 6% and 9%. For 0% and 3% NaCl concentrations, JU-33 (84.37 mg/L for 0% NaCl and 130.36 mg/L for 3% NaCl) showed higher P-solubilising efficiency than JU-24 (73.29 mg/L for 0% NaCl and 87.42 mg/L for 3% NaCl) for both NaCl concentrations when inoculated in Ca3(PO4)2 containing liquid medium. In media containing AlPO4 and FePO4 without NaCl, the P-solubilising activity of JU-24 is higher than JU-33 for these two substrates. Moreover, these strains showed noticeable levels of P solubilisation activity in the presence of various carbon sources indicating high P-solubilising efficacy. The soil inoculation experiment revealed that inoculating the experimental soil with JU-33 resulted in an obvious increase in available P, which increased from 13.08 mg/L in the non-inoculated soil to 18.40 mg/L in the inoculated soil with the bacterial isolate, JU-33. This study clearly showed that JU-24 and JU-33 isolates could be used as biofertilizers in ecological agricultural systems and may help to sustain environmental health and soil productivity. The use of biofertilizers can reduce the use of expensive chemical fertilisers, reducing planting costs and improving soil fertility through long-term use. Biofertilizers can help solve the problem of feeding an increasing global population at a time when agriculture is facing various environmental stresses and are affordable for low-income farmers.

Характеристика продуктивности дрожжей Candida ethanolica штамма BKM Y-2300 T

In the modern world, the applying of microorganisms as producers of various valuable compounds is relevant. Such producers are often yeast Candida, which are used to synthesize various products – proteins, enzymes, vitamins. One of the representatives of the genus, Candida ethanolica, is interesting because it uses ethanol as a carbon source. Synthetic ethanol is a convenient raw material for the biotechnological process, since it has a lower cost compared to chemically pure carbohydrates, is well water-soluble and does not contain impurities. Since the C. ethanolica is insufficiently studied as a biotechnological object, the aim of the research was the obtaining new information about the strain Candida ethanolica (BKM strain Y-2300 T). The main morphological, cultural, physiological and biochemical properties of the yeast strain were studied. Part of them turned out to be typical for most yeast of genus Candida. In addition, the strain was facultatively anaerobic with respect to oxygen. In addition, the most suitable carbon source and its optimal concentration were selected for this strain. It showed the greatest preference to ethanol when grown in the presence of various carbon sources (carbohydrates, alcohols, oils). The biggest increasing of cell number and biomass was observed if an ethanol content in the medium was of 1.5% vol. The optimal conditions for laboratory cultivation for this strain were determined: aeration degree (200 rpm); temperature 37 ° C; pH of the medium (7.0). The yeast were resistant to salt concentrations from 4.5 to 5.0%. The strain was also tested for the activity of some enzymes important in the food and processing industry: saccharolytic, proteolytic, lipolytic, amylolytic, catalase, and urease. The most active enzymes were that hydrolyze sucrose, lipids and proteins. The ability of C. ethanolica to intracellular synthesis of protein, carbohydrates and vitamins was evaluated. This strain formed a small amount of carbohydrates and vitamins, but its protein quantity was quite substantial. The maximum amount of protein in the cells accumulated after 4 hours (from the start of cultivation) and was 31.10 %. This value was at the level of some well-known producers of cell protein. Thus, the studied strain is a potentially valuable producer for the biotechnology industry as a source of cell protein, glycosidase, lipase and protease. Further studies that are more specific are required to exploit the biosynthetic potential of this strain in industry.

Characterization of a mesophilic actinobacteria that degrades poly(butylene adipate-co-terephthalate)

An aliphatic aromatic copolyester, poly(butylene adipate-co-terephthalate) (PBAT) is a chemically synthetic and biodegradable polymer that exhibits good mechanical properties, similar to those of low-density polyethylene (LDPE), and can be a replacement for LDPE as biodegradable mulch films in the agricultural field. Biodegradability of PBAT is stable at high temperature conditions (50 – 60 ˚C) such as compost environments compared to mild temperature conditions (25 – 37 ˚C) such as soil environments. Considering that PBAT could be used in biodegradable agricultural applications such as mulching film, it is important to investigate the biodegradation mechanism at mild temperatures. In this study, a PBAT-degrading bacterium isolated from a soil environment, designated as strain NKCM 2511, was studied in detail. Genetic and biochemical analysis revealed that the strain belongs to the genus Rhodococcus in the phylum Actinobacteria. The strain grew only in aerobic conditions and formed a clear zone on a PBAT containing plate in the temperature range of 20 ˚C to 30 ˚C. Based on biochemical oxygen demand (BOD) biodegradation testing, among 3 PBAT components, adipicacid and terephthalic acid resulted in low growth rate of the strains (5 % and 7 %, incubated at 25 °C for 20 days), whereas 1,4-butanediol resulted in good growth of the strains (55 %). The low BOD biodegradation rate of PBAT by this strain (7 %) may be due to such low rates of terephthalic and adipic acid. Additionally, the PBAT degradation rate was proportional to the growth rate in the presence of various carbon sources. Therefore, the strain was an aerobically mesophilic PBAT-degrading bacterium that expressed the PBAT-degrading enzyme constitutively. To our knowledge, this is the first report on a PBAT-degrading actinobacterial strain in mild conditions. This study provides information to better understand the biodegradation mechanism of PBAT under mild conditions such as in fields.

A LysR-Type Transcriptional Regulator LcrX Is Involved in Virulence, Biofilm Formation, Swimming Motility, Siderophore Secretion, and Growth in Sugar Sources in Xanthomonas axonopodis Pv. glycines

Xanthomonas axonopodis pv. glycines (Xag) is a Gram-negative bacterium that causes bacterial pustule disease in soybean. To acclimate to new environments, the expression of genes in bacteria is controlled directly or indirectly by diverse transcriptional factors. Among them, LysR type transcriptional regulators are well-characterized and abundant in bacteria. In a previous study, comparative proteomic analysis revealed that LysR type carbohydrate-related transcriptional regulator in Xag (LcrX) was more abundant in XVM2, which is a minimal medium, compared with a rich medium. However, the functions of LcrX in Xag have not been characterized. In this study, we generated an LcrX-overexpressing strain, Xag(LcrX), and the knockout mutant strain, XagΔlcrX(EV), to elucidate the functions of LcrX. Bacterial multiplication of Xag(LcrX) in soybean was significantly impaired, indicating that LcrX is related to virulence. Comparative proteomic analysis revealed that LcrX is mainly involved in carbohydrate metabolism/transport and inorganic ion transport/metabolism. Based on the results of proteomics analysis, diverse phenotypic assays were carried out. A gel electrophoresis mobility shift assay demonstrated that LcrX specifically bound to the putative promoter regions of genes encoding putative fructose 1,6-bisphosphatase and protease. Through a 96-well plate assay under various conditions, we confirmed that the growth of Xag(LcrX) was dramatically affected in the presence of various carbon sources, while the growth of XagΔlcrX(EV) was only slightly changed. Biofilm formation activity was reduced in Xag(LcrX) but enhanced in XagΔlcrX(EV). The production of siderophores was also decreased in Xag(LcrX) but not altered in XagΔlcrX(EV). In contrast, LcrX was not associated with exopolysaccharide production, protease activity, or bacterial motility. These findings provide new insights into the functions of a carbohydrate-related transcriptional regulator in Xag.

Optimization and characterization of bioplastic produced by bacillus cereus

Bioplastics can be defined as plastics made of biomass such as corn, sugarcane etc. These substances have been increasingly spotlighted as means to saving fossil fuels, reducing CO2 emission and plastic wastes. Biodegradability of Bioplastics has been widely publicized in society and the demand for packaging is rapidly increasing among retailers and the food industry at large scale. The plastic which is available in market is very dangerous as it is non-biodegradable. Therefore, it is the demand of the day that biodegradable plastics should be produced and used. The present review highlights all these points regarding the applications, production, types, challenges, sustainability, fermentation, process development and use of cheap substrates for bioplastics production. The bacterial isolate Bacillus cereus SE-1 was found to possess a higher level of PHB production in presence of various carbon sources used. However, a higher level of production was obtained with maltose (5.63 g/l) and a lower production was obtained when dextrose (0.4 g/l) was used as sole carbon source. FTIR analysis reveals that, the extracted PHB possesses the same pattern of functional groups as that of the standard PHB i.e. the characteristics presence of –OH and –C=O stretching. In order to increase the potential use of the extracted PHB, it was blended with thermoplastic starch under experimental conditions. After blending, the crystalline nature of the product was highly increased as the diffraction patterns were observed at 2e values of 26.80°, 31.74°, 45.59°, and 56.22°. Thus, the bacterial mediated PHB synthesis can be used as a better alternative to deal with the currently available practices of plastic use and its gradually increasing pollution level.

Autoclaved mycelium induces efficiently the production of hydrolytic enzymes for protoplast preparation of autologous fungus

The production of hydrolytic enzymes by the mutant Trichoderma reesei Rut-C30 when cultivated in the presence of various carbon sources: glucose, wheat bran and autoclaved mycelium of Penicillium occitanis CT1 has been studied. Glucose was shown to repress all studied hydrolases, 3% of either wheat bran or autoclaved cell walls led to high titers of enzymes, and were favorably comparable to commercial lysing enzymes (LE). The lysing enzyme cocktail obtained when T. reesei Rut-C30 was cultivated in the presence of autoclaved P. occitanis CT1 mycelia appeared to be a most effective for P. occitanis CT1 protoplast formation. Maximal yield of protoplasts reached 13 × 106 protoplasts/mL while commercial LE preparation released only 4 × 106 protoplasts/mL. The protoplast yield was affected also by the osmotic stabilizer, with KCl giving the best results. Our results suggest that to achieve the best protoplastization rate, the enzyme preparation should be obtained following induction by the autoclaved mycelium of the autologous fungus.

A novel high molecular weight thermo-acidoactive β-glucosidase from Beauveria bassiana

An extracellular high molecular weight β-glucosidase was secreted by a local strain P1 of Beauveria bassiana. The enzyme was produced in the presence of various carbon sources, namely glucose, maltose, lactose, glycerol, starch, wheat bran and gruel. The highest level of β-glucosidase activity was produced with wheat bran at the concentration of 3%. Glucose caused a repressor effect on the β-glucosidase expression in a dose-dependent manner. The highest enzyme production level was obtained at initial pH of 6.0 and 7.0 in the culture medium. The zymography analysis revealed that B. bassiana secreted a β-glucosidase with high molecular weight between 400 and 600 kDa. The enzymatic preparation was characterized and showed temperature and pH optima of 55°C and 5.0, respectively. The enzyme was stable at 40 and 50°C but its stability declined at 60°C. Interestingly, this β-glucosidase had high stability at acid and basic pH saving its initial activity after 24 h incubation at pH from 3.0 to 11.0. It was stable also in presence of monovalent Na+ and K+ ions saving 60% of its initial activity at 2 M salts. Bivalent metal ions preserved totally or partially the enzymatic activity; in addition, Ba2+ was revealed as an activator. This is the first report that focuses on the production and the biochemical characterization of a β-glucosidase from the entomopathogenic fungus, B. bassiana.

Production of cellulase from Aspergillus terreus MS105 on crude and commercially purified substrates.

Aspergillus terreus MS105 was originally isolated from soil and screened for cellulase production in the presence of various carbon sources including carboxymethyl cellulose (CMC), avicel, sigmacell, filter-paper and salicin. CMC induced the production of endoglucanase (EG) and filter-paperase while the levels of β-glucosidase (BGL) were increased when salicin was present in the medium. Nature of production medium influenced the duration of lag- and log-phase of the growth, rate of fungal dry-mass and enzyme production. The volumetric and specific productivity of cellulase under submerged fermentation of grass were 1.7–20-folds higher than sugarcane-bagasse, corncob and commercially available purified substrates. Nonetheless, solid state fermentation (SSF) of crude substrates also yielded high volumetric productivity of EG and BGL. The studies on characterization of enzymes showed that EG was more thermostable than BGL with an optimum activity at 70 °C and a melting temperature of 76 °C. A 1.2–1.5-folds increase in EG activity was observed in the presence of K+, Ca2+ and Mg2+, whereas, the EG and BGL activities remained unaffected in the presence of EDTA. Both the enzyme activities performed optimally under acidic range of pH.

Medium Initial pH and Carbon Source Stimulate Differential Alkaline Cellulase Time Course Production in Stachybotrys microspora

The production profile of cellulases of the mutant strain A19 from the filamentous fungus Stachybotrys microspora was studied in the presence of various carbon sources (glucose, lactose, cellulose, carboxymethylcellulose (CMC), and wheat bran) and a range of medium initial pH (5, 7, and 8). Two extracellular cellulases from the Stachybotrys strain (endoglucanases and β-glucosidases) were monitored by enzymatic assay, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and zymogram analysis. Glucose and lactose repressed CMCase time course production while they permitted a strong β-glucosidase one. On Avicel cellulose, CMC, and wheat bran, both activities were highly produced. Wheat bran (WB) is the best carbon source with an optimum of production at days 5 and 6. The production kinetics of both activities were shown to depend on the medium initial pH, with a preference for neutral or alkaline pH in the majority of conditions. The exception concerned the β-glucosidase which was much more produced at acidic pH, on glucose and cellulose. Most interestingly, a constitutive and conditional expression of an alkaline endoglucanase was revealed on the glucose-based medium at an initial pH of 8 units. The zymogram analysis confirmed such conclusions and highlighted that carbon sources and the pH of the culture medium directed a differential induction of various endoglucanases and β-glucosidases.

The Vibrio cholerae Mannitol Transporter Is Regulated Posttranscriptionally by the MtlS Small Regulatory RNA

Vibrio cholerae continues to pose a health threat in many developing nations and regions of the world struck by natural disasters. It is a pathogen that rapidly adapts to aquatic environments and the human small intestine. Small regulatory RNAs (sRNAs) may contribute to this adaptability. Specifically, the mannitol operon sRNA (MtlS sRNA; previously designated the IGR7 sRNA) is transcribed antisense to the 5' untranslated region of the mtl operon, encoding the mannitol-specific phosphotransferase system. Mannitol is a six-carbon sugar alcohol that accumulates in the human small intestine, the primary site of V. cholerae colonization. To better understand the V. cholerae mtl operon at a molecular level, we investigated mtlA expression in the presence of various carbon sources and the role of the MtlS sRNA. We observed that MtlA protein is present only in cells grown on mannitol sugar, whereas MtlS sRNA is expressed during growth on all sugars other than mannitol. In contrast, mtlA mRNA is expressed in similar amounts regardless of the carbon source used for bacterial growth. These observations suggest that the regulation of MtlA protein expression is a posttranscriptional event. We further demonstrate that MtlS sRNA overexpression repressed MtlA synthesis without affecting the stability of the messenger and that this process is largely independent of Hfq. We propose a model in which, when carbon sources other than mannitol are present, MtlS sRNA is transcribed, base pairs with the 5' untranslated region of the mtlA mRNA, occluding the ribosome binding site, and inhibits the synthesis of the mannitol-specific phosphotransferase system.

Production of novel platycodin D derivatives by Aspergilli

Platycodin D (PD) is the major saponin components abundant in the root of Platycodon grandiflorum, which has been reported to have anti‐inflammatory and anti‐tumor activities. PD contains sugar residues including glucose unit at C‐3 and apiose‐xylose‐rhamnose‐arabinose residue at C‐28. In the present study, 8 noble PD derivatives with diverse sugar chains were produced by the crude enzyme extracts of Aspergillus niger and A. usamii grown in the presence of various carbon sources. Commercially available enzymes such as hesperidinase, β‐glucosidase, and β‐xylosidase were not effective in cleaving the glycosidic side chains of PD. Depending on the sugar side chains the PD derivatives demonstrated different degree of toxicity against a normal fetal colon cell line. These findings could be informative to obtain novel PD derivatives with reduced cytotoxicity by Aspergilli. This work was supported by Industrialization Support Program for Bio‐technology of Agriculture and Forestry, Ministry for Food, Agriculture, Forestry and Fisheries (810007‐03‐1‐WT211), Republic of Korea.

Renewable biomass production by mixotrophic algae in the presence of various carbon sources and wastewaters

This study evaluated mixotrophic growth potential of native microalgae in media supplemented with different organic carbon substrates and wastewaters. Three robust mixotrophic microalgae viz. Chlamydomonas globosa, Chlorella minutissima and Scenedesmus bijuga were isolated after long-term enrichments from industrial wastewater. The mixotrophic growth of these microalgae resulted in 3–10 times more biomass production relative to phototrophy. Glucose, sucrose and acetate supported significant mixotrophic growth. Poultry litter extract (PLE) as growth medium recorded up to 180% more biomass growth compared to standard growth medium BG11, while treated and untreated carpet industry wastewaters also supported higher biomass, compared to BG11 growth with no significant effect of additional nitrogen supplementation. Supplementing treated wastewater and PLE with glucose and nitrogen resulted in 2–7 times increase in biomass relative to the unamended wastewaters or PLE. The consortia of Chlamydomonas–Chlorella and Scenedesmus–Chlorella were the best for PLE and untreated wastewater respectively, while a combination all three strains was suitable for both PLE and wastewater. These algae can be good candidates for biofuel feedstock generation as they would not require freshwater or fertilizers. Such mixotrophic algal consortia offer great promise for production of renewable biomass for bioenergy applications using wastewaters.

Novel food-grade plasmid vector based on melibiose fermentation for the genetic engineering of Lactococcus lactis.

The alpha-galactosidase gene (aga) and a gene coding for a putative transcriptional regulator from the LacI/GalR family (galR) of Lactococcus raffinolactis ATCC 43920 were cloned and sequenced. When transferred into Lactococcus lactis and Pediococcus acidilactici strains, aga modified the sugar fermentation profile of the strains from melibiose negative (Mel(-)) to melibiose positive (Mel(+)). Analysis of galA mutants of L. lactis subsp. cremoris MG1363 indicated that the putative galactose permease GalA is also needed to obtain the Mel(+) phenotype. Consequently, GalA may also transport melibiose into this strain. We demonstrated that when aga was associated with the theta-type replicon of a natural L. lactis plasmid, it constituted the selectable marker of a cloning vector named pRAF800. Transcriptional analysis by reverse transcriptase PCR suggests that this vector is also suitable for gene expression. The alpha-galactosidase activity conferred by pRAF800 was monitored in an industrial strain grown in the presence of various carbon sources. The results indicated that the enzymatic activity was induced by galactose and melibiose, but not by glucose or lactose. The gene encoding the phage defense mechanism, AbiQ, was cloned into pRAF800, and the resulting clone (pRAF803) was transferred into an industrial L. lactis strain that became highly phage resistant. The measurements of various growth parameters indicated that cells were not affected by the presence of pRAF803. Moreover, the plasmid was highly stable in this strain even under starter production conditions. The L. raffinolactis aga gene represents the basis of a novel and convenient food-grade molecular tool for the genetic engineering of lactic acid bacteria.

An alternate carbon source for enhancing production of polysaccharides by Silene vulgaris callus

Pectin termed silenan and acidic arabinogalactan were isolated as cell-wall polysaccharides of Silene vulgaris callus in the presence of various carbon sources as components of the media. The maximum yields, productivity per litre of medium and production per day of acidic arabinogalactan, were achieved using glucose or galactose as the carbon source. Sucrose was found to increase the production of the polysaccharides. Yields, productivity and rate of production of arabinogalactan per day were decreased in the presence of arabinose. Yields of silenan, productivity and rate of production per day were closely related irrespective of the sugar used as the carbon source in the media (sucrose, glucose or galactose) and yields of silenan from the callus growing on arabinose were comparable. A concentration of sucrose in the 20–50 g/L range enhanced the biosynthesis of silenan and at 50 g/L the silenan contained the linear backbone and the ramified regions of the macromolecule.

A comparison of carbon source utilization for growth and nitrogenase activity in two Frankia isolates

The carbon source requirements for the growth and nitrogen fixation of two morphologically distinct Frankia isolates were examined. Isolate ArI3 (from Alnus rubra) grew well on propionate, malate, acetate, and trehalose, and isolate CcI2 (from Casuarina cunninghamiana) grew best on pyruvate, acetate, and propionate. In general, the same carbon sources that supported growth supported both the development of vesicles and nitrogenase activity in long-term induction experiments in both isolates. However, ArI3 cultures induced on proprionate had 7 to 26 times the activity of other carbon sources and ArI3 cultures induced on acetate did not develop any detectable acetylene reduction. In a parallel set of experiments, cultures of both isolates were induced for nitrogenase activity on propionate and the resulting nitrogen fixing cultures were washed free of the organic acid by centrifugation. The washed cultures were incubated in the presence of various carbon sources to determine the ability of a particular substrate to supply energy directly for nitrogen fixation when vesicles and nitrogenase were already present. As was observed in the long-term induction experiments, pyruvate, propionate, and acetate supported the greatest activity in CcI2. Succinate and malate supported the greatest activity in ArI3, and propionate had very little stimulation of acetylene reduction. The reason for the lack of stimulation by propionate for washed cells of ArI3 was unclear but may have been due to toxic concentrations of the organic acid. In an attempt to compare the carbon utilization of ArI3 in pure culture with that in the alder symbiosis, oxygen uptake in the presence of various carbon sources of vesicles clusters isolate from Alnus rubra nodules inoculated with ArI3 was compared with the oxygen uptake of nitrogen-fixing pure cultures of ArI3. The oxygen uptake of the isolated vesicle clusters was stimulated by sucrose, trehalose, and glucose, but not by a variety of organic acids. In comparison, nitrogen-fixing pure cultures of ArI3 readily oxidized sugars and organic acids.

Effect of temperature on violacein production in a psychrotrophicChromobacterium from Lake Ontario sediment

A truly psychrotrophic strain ofChromobacterium, which was isolated from Lake Ontario sediment and characterized asChromobacterium lividum, was found to be capable of pigment production that was completely prevented at 0°C, although growth readily occurred. Normal pigment formation occurred at 15°C, 20°C, and 25°C. The prevention of synthesis of the pigment at 0°C, which was confirmed spectrophotometrically to be violacein, was not reversed by the presence of various carbon sources, although all except one acted as growth substrates. In addition, some of the carbon sources actually inhibited pigment production at 20°C, preventing violacein synthesis in the presence of pyruvate which was shown to allow pigmentation. Similar results were obtained under both liquid and solid media cultivation conditions.