Peptone-yeast Extract Medium Research Articles

Role of PhoP-PhoQ Two-Component System in Biofilm Formation of the Phytopathogen <i>Dickeya dadantii</i> Strain 3937

To elucidate the role of PhoP-PhoQ two-component system in biofilm formation by the phytopathogen Dickeya dadantii (formerly Erwinia chrysanthemi) strain 3937, we used marker-exchanged mutants deficient in both phoP and phoQ. A biofilm-inducing medium, salt-optimized broth plus glycerol (SOBG) which contains salt-optimized broth (SOB) plus 2% of glycerol, supported biofilm formation by D. dadantii strain 3937 to a greater extent than either M63 glycerol minimal medium or yeast extract peptone (YP) medium or Luria-Bertani (LB) medium. In addition, magnesium greatly induced biofilm formation. It was found that both the phoP and phoQ mutants exhibited enhanced ability to form a biofilm on the surface of the glass test tube as compared to the wild-type strain in SOBG medium containing high concentration of magnesium. In addition, under high magnesium condition, both the mutants produced elevated level of exopolysaccharide. Accordingly, genes responsible for exopolysaccharide production (weaP, wza and wzc) were derepressed in the mutants. These results suggest that the PhoP-PhoQ two-component system may regulate formation of biofilm, at least in part, by transcriptional control of genes responsible for exopolysaccharide biosynthesis of D. dadantii strain 3937. Since biofilm-associated bacteria showed more tolerance to acidic pH and high osmotic stress, it is apparent that the formation of biofilm may be an important factor for the survival of D. dadantii strain 3937 in unfavorable environment.

Vibrio sp. DSM 14379 Pigment Production—A Competitive Advantage in the Environment?

The ability to produce several antibacterial agents greatly increases the chance of producer's survival. In this study, red-pigmented Vibrio sp. DSM 14379 and Bacillus sp., both isolated from the same sampling volume from estuarine waters of the Northern Adriatic Sea, were grown in a co-culture. The antibacterial activity of the red pigment extract was tested on Bacillus sp. in microtiter plates. The MIC(50) for Bacillus sp. was estimated to be around 10⁻⁵ mg/L. The extract prepared form the nonpigmented mutant of Vibrio sp. had no antibacterial effect. The pigment production of Vibrio sp. was studied under different physicochemical conditions. There was no pigment production at high or low temperatures, high or low salt concentrations in peptone yeast extract (PYE) medium, low glucose concentration in mineral growth medium or high glucose concentration in PYE medium. This indicates that the red pigment production is a luxurious good that Vibrio sp. makes only under favorable conditions. The Malthusian fitness of Bacillus sp. in a co-culture with Vibrio sp. under optimal environmental conditions dropped from 4.0 to -7.6, which corresponds to three orders of magnitude decrease in the number of CFU relative to the monoculture. The nonpigmented mutant of Vibrio sp. in a co-culture with Bacillus sp. had a significant antibacterial activity. This result shows that studying antibacterial properties in isolation (i.e. pigment extract only) may not reveal full antibacterial potential of the bacterial strain. The red pigment is a redundant antibacterial agent of Vibrio sp.

Corncob-Induced endo-1,4-β-d-Xylanase of Aspergillus oryzae MTCC 5154: Production and Characterization of Xylobiose from Glucuronoxylan

Eight different fungi were cultivated in a peptone-yeast extract medium containing 1% oat spelt xylan (OSX) to evaluate endo-1,4-beta-xylanase secretion for xylooligosaccharide (XOS) production. Aspergillus oryzae MTCC 5154, Aspergillus flavus , Aspergillus niger , and Aspergillus ochraceus showed significant titers of endoxylanases, which were further used for the production of XOS from birch wood xylan (BWX). A. oryzae produced 89.5 +/- 1.13% XOS in the hydrolysate at 24 h of reaction. The effect of OSX, BWX, and raw corncob on the induction of endoxylanase in A. oryzae was studied, and the xylanase activity was maximum at 96 h of cultivation in 3% corncob containing medium. XOS produced at 36 h of reaction was 5.87 +/- 0.53 mg/mL (12 +/- 2% xylose, 48 +/- 2.43% xylobiose, and 40 +/- 3.6% higher oligomers) from 1% BWX . HPLC/refractive index detection and ESI/MS analysis of fractions obtained by GPC corresponded to neutral and 4- O-methyl-alpha- d-glucuronic acid substituted acidic oligosaccharides. The major fraction, beta- d-xylopyranosyl-(1-->4)- d-xylanopyranose was characterized using (13)C NMR.

Atypical Internal Yellowing of Papaya Fruit in Hawaii Caused by Enterobacter sakazakii

Internal yellowing (IY) caused by Enterobacter cloacae and characterized by yellow discolored tissue surrounding the papaya (Carica papaya L.) seed cavity, diffuse margins, and the presence of a distinctly rotten odor was first reported in 1987 (3). Here we report the formation of atypical internal yellowing (AIY) in ripe papaya caused by the bacterium Enterobacter sakazakii. In surveys conducted from 2006 to 2007, 'Kapoho Solo' papayas grown in the Puna District of Hawaii Island were obtained from various packinghouses. After incubation at 27°C, the papayas were bisected and examined for symptoms of IY. Among papayas that were asymptomatic for IY, a dull, greenish yellow discoloration of the flesh with a distinct margin extending from the seed cavity into the pericarp was noted, along with a pungent odor. These symptoms occurred in 5 of the 500 fruit surveyed and bacterial populations were 102 to 103 CFU/g. Discolored tissue was aseptically excised, weighed, macerated, serially diluted in sterile distilled water (SDW), and plated onto modified peptone yeast extract medium (PT-M4) (4). The plates were incubated at 30°C for 24 to 48 h until single colonies were evident. After 48 h, colonies on PT-M4 were orange-red, convex and circular, and surrounded by a somewhat opaque 1-mm margin. After single colony purification, five strains were obtained. The strains, inoculated into oxidation/fermentation-glucose tubes and API 20E strips (bioMerieux, Inc., Durham, NC) incubated at 30°C, were shown to be facultative anaerobes and identified as E. sakazakii with a 98.4% certainty. Colonies plated onto tryptic soy agar (TSA) and incubated for 72 h at 25°C produced yellow pigmentation, indicative of E. sakazakii. Amplification by PCR with E. sakazakii-specific primers (2) yielded a 929-bp fragment, which was absent with E. cloacae and Pseudomonas aeruginosa template DNA. To confirm pathogenicity, cell suspensions at 109 CFU/ml of putative E. sakazakii strains RK07-05, RK07-06, and RK07-07 and E. cloacae (3) were inoculated by injection (0.5 ml per site) into one-third-ripe 'Kapoho Solo' papayas (six fruit per strain, inoculated at duplicate sites) and incubated at 27°C for 4 days. Control sites were injected with 0.5 ml of SDW. Fruit inoculation experiments were repeated. E. cloacae-inoculated sites produced typical IY as previously described (3), while the sites inoculated with the three E. sakazakii strains produced greenish yellow tissue (26% mean incidence), symptomatic of AIY. Control sites did not produce IY or AIY. Koch's postulates were fulfilled, and the identification of reisolated bacterial strains was confirmed with API 20E, PCR, and pigment production on TSA. Although less prevalent (1% incidence) than the typical IY produced by E. cloacae (3), E. sakazakii has the potential to affect quality and food safety of fresh and processed papaya products. E. sakazakii has been implicated in a severe form of neonatal meningitis, sepsis, and necrotizing enterocolitis (1). Research into the transmission and infection of papaya of this cross-domain pathogen merits further study.

Cwc24p, a Novel Saccharomyces cerevisiae Nuclear Ring Finger Protein, Affects Pre-snoRNA U3 Splicing

U3 snoRNA is transcribed from two intron-containing genes in yeast, snR17A and snR17B. Although the assembly of the U3 snoRNP has not been precisely determined, at least some of the core box C/D proteins are known to bind pre-U3 co-transcriptionally, thereby affecting splicing and 3'-end processing of this snoRNA. We identified the interaction between the box C/D assembly factor Nop17p and Cwc24p, a novel yeast RING finger protein that had been previously isolated in a complex with the splicing factor Cef1p. Here we show that, consistent with the protein interaction data, Cwc24p localizes to the cell nucleus, and its depletion leads to the accumulation of both U3 pre-snoRNAs. U3 snoRNA is involved in the early cleavages of 35 S pre-rRNA, and the defective splicing of pre-U3 detected in cells depleted of Cwc24p causes the accumulation of the 35 S precursor rRNA. These results led us to the conclusion that Cwc24p is involved in pre-U3 snoRNA splicing, indirectly affecting pre-rRNA processing.

Dependence of the cytotoxicity of multi-walled carbon nanotubes on the culturemedium

This study examined the influence of multi-walled carbon nanotubes (MWNTs) on thegrowth of the unicellular protozoan Tetrahymena pyriformis. Contrary to thefindings from most other investigations, our experiment indicated that MWNTsstimulated growth of the cells cultured in proteose peptone yeast extract medium(PPY). Atomic force microscopy images and thermogravimetric analysis showed thespontaneous formation of peptone–MWNT conjugates in the medium by noncovalentbinding. Uptake of large amounts of the conjugates by Tetrahymena pyriformis wasresponsible for growth stimulation, evidenced by images with fluorescently labelledpeptone. After the PPY medium was replaced by a filtrated pond water medium(FPW), however, inhibition of the growth of cells exposed to MWNTs occurred.Measurements of the level of malondialdehyde and superoxide dismutase activitydemonstrated further that MWNTs might be either toxic or nontoxic, depending on themedium used to cultivate Tetrahymena pyriformis. The biological effects of theinteraction of MWNTs with some composites in culture media would be helpfulfor understanding the mechanisms of the toxicity of carbon nanotubes to livingsystems.

Effects of lipid composition on the membrane activity and lipid phase behaviour of Vibrio sp. DSM14379 cells grown at various NaCl concentrations

The membrane lipid composition of living cells generally adjusts to the prevailing environmental and physiological conditions. In this study, membrane activity and lipid composition of the Gram-negative bacterium Vibrio sp. DSM14379, grown aerobically in a peptone-yeast extract medium supplemented with 0.5, 1.76, 3, 5 or 10% (w/v) NaCl, was determined. The ability of the membrane to reduce a spin label was studied by EPR spectroscopy under different salt concentrations in cell suspensions labeled with TEMPON. For lipid composition studies, cells were harvested in a late exponential phase and lipids were extracted with chloroform–methanol–water, 1:2:0.8 (v/v). The lipid polar head group and acyl chain compositions were determined by thin-layer and gas–liquid chromatographies. 31P-NMR spectroscopy was used to study the phase behaviour of the cell lipid extracts with 20 wt.% water contents in a temperature range from −10 to 50 °C. The results indicate that the ability of the membrane to reduce the spin label was highest at optimal salt concentrations. The composition of both polar head groups and acyl chains changed markedly with increasing salinity. The fractions of 16:0, 16:1 and 18:0 acyl chains increased while the fraction of 18:1 acyl chains decreased with increasing salinity. The phosphatidylethanolamine fraction correlated inversely with the lysophosphatidylethanolamine fraction, with phosphatidylethanolamine exhibiting a minimum, and lysophosphatidylethanolamine a maximum, at the optimum growth rate. The fraction of lysophosphatidylethanolamine was surprisingly high in the lipid extracts. This lipid can form normal micellar and hexagonal phases and it was found that all lipid extracts form a mixture of lamellar and normal isotropic liquid crystalline phases. This is an anomalous behaviour since the nonlamellar phases formed by total lipid extracts are generally of the reversed type.

Transcriptional profiling of Caulobacter crescentus during growth on complex and minimal media.

Microarray analysis was used to examine gene expression in the freshwater oligotrophic bacterium Caulobacter crescentus during growth on three standard laboratory media, including peptone-yeast extract medium (PYE) and minimal salts medium with glucose or xylose as the carbon source. Nearly 400 genes (approximately 10% of the genome) varied significantly in expression between at least two of these media. The differentially expressed genes included many encoding transport systems, most notably diverse TonB-dependent outer membrane channels of unknown substrate specificity. Amino acid degradation pathways constituted the largest class of genes induced in PYE. In contrast, many of the genes upregulated in minimal media encoded enzymes for synthesis of amino acids, including incorporation of ammonia and sulfate into glutamate and cysteine. Glucose availability induced expression of genes encoding enzymes of the Entner-Doudoroff pathway, which was demonstrated here through mutational analysis to be essential in C. crescentus for growth on glucose. Xylose induced expression of genes encoding several hydrolytic exoenzymes as well as an operon that may encode a novel pathway for xylose catabolism. A conserved DNA motif upstream of many xylose-induced genes was identified and shown to confer xylose-specific expression. Xylose is an abundant component of xylan in plant cell walls, and the microarray data suggest that in addition to serving as a carbon source for growth of C. crescentus, this pentose may be interpreted as a signal to produce enzymes associated with plant polymer degradation.

The extracellular constitutive production of chitin deacetylase in Metarhizium anisopliae: possible edge to entomopathogenic fungi in the biological control of insect pests

The possible contribution of extracellular constitutively produced chitin deacetylase by Metarhizium anisopliae in the process of insect pathogenesis has been evaluated. Chitin deacetylase converts chitin, a β-1,4-linked N-acetylglucosamine polymer, into its deacetylated form chitosan, a glucosamine polymer. When grown in a yeast extract–peptone medium, M. anisopliae constitutively produced the enzymes protease, lipase, and two chitin-metabolizing enzymes, viz. chitin deacetylase (CDA) and chitosanase. Chitinase activity was induced in chitin-containing medium. Staining of 7.5% native polyacrylamide gels at pH 8.9 revealed CDA activity in three bands. SDS–PAGE showed that the apparent molecular masses of the three isoforms were 70, 37, and 26 kDa, respectively. Solubilized melanin (10 μg) inhibited chitinase activity, whereas CDA was unaffected. Following germination of M. anisopliae conidia on isolated Helicoverpa armigera, cuticle revealed the presence of chitosan by staining with 3-methyl-2-benzothiazoline hydrazone. Blue patches of chitosan were observed on cuticle, indicating conversion of chitin to chitosan. Hydrolysis of chitin with constitutively produced enzymes of M. anisopliae suggested that CDA along with chitosanase contributed significantly to chitin hydrolysis. Thus, chitin deacetylase was important in initiating pathogenesis of M. anisopliae softening the insect cuticle to aid mycelial penetration. Evaluation of CDA and chitinase activities in other isolates of Metarhizium showed that those strains had low chitinase activity but high CDA activity. Chemical assays of M. anisopliae cell wall composition revealed the presence of chitosan. CDA may have a dual role in modifying the insect cuticular chitin for easy penetration as well as for altering its own cell walls for defense from insect chitinase.

Effectiveness of peptone-yeast extract (P-Y) medium in the cultivation and isolation of Entamoeba histolytica/Entamoeba dispar in Turkish patients

Amebiasis is a common protozoan infection worldwide, causing serious health problems in both children and adults. Today, almost 10% of the world population is infected with Entamoeba histolytica/Entamoeba dispar. The aims of this study were both the comparison of the reproduction rates and densities of E. histolytica/E. dispar in Robinson, Dobell-Laidlaw and P-Y culture media and isolation of E. histolytica/E. dispar from stool samples in Peptone-Yeast (P-Y) medium. Trophozoites and cysts of E. histolytica/E. dispar, maintained in Robinson medium, and stool samples of patients with amebiasis were inoculated into P-Y, Robinson and Dobell-Laidlaw culture media. Reproduction rates reached their peak levels 48 h after the inoculation in all culture media. Reproduction rates in P-Y and Robinson media were found similar; however, they were higher than the reproduction rate in Dobell-Laidlaw medium ( p < 0.01); there was no statistically significant difference between the reproduction rates of P-Y and Robinson media ( p > 0.05). Twelve isolates from 12 patients were cultivated in P-Y medium and checked for reproduction everyday for 7 days. Twelve of the 12 (100%) isolates were cultivated in P-Y medium, indicating that the P-Y was an effective medium for the isolation of E. histolytica/E. dispar in stool samples. According to these results, P-Y medium could be preferred in immunologic, serologic and molecular studies and, thus the definitive diagnosis of amebiasis due to its low cost and simple formula.

Crithidia guilhermei: gelatin- and haemoglobin-degrading extracellular metalloproteinases

The extracellular metalloproteinases of the insect trypanosomatid Crithidia guilhermei were characterized through the incorporation of different protein substrates (gelatin, casein, haemoglobin, and bovine serum albumin) into SDS–PAGE. Two gelatinases (60 and 80 kDa) showed ability to degrade casein as well and a 67-kDa enzyme presented the broadest specificity since it was also able to degrade casein and haemoglobin. Besides the 67-kDa extracellular proteinase detected on haemoglobin-SDS–PAGE, a 43-kDa haemoglobinase was only observed with this substrate. All C. guilhermei proteinases were incapable of using bovine serum albumin. C. guilhermei was also grown in four different culture media and the best proteinase production was reached using yeast extract-peptone medium containing glucose as the major carbon source. The results point to the importance of the use of distinct culture media and proteinaceous substrates on the characterization of extracellular proteolytic activities in trypanosomatids, since alterations in growth conditions and methods of detection could lead to distinct proteolytic profiles. Index Descriptors and Abbreviations: Crithidia guilhermei; trypanosomatid; extracellular proteinases; culture media; protein substrates; sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE); dl-Dithiothreitol (DTT); trans-epoxysuccinyl- l-leucylamido-(4-guanidino)-butane (E-64); phenylmethyl-sulfonyl fluoride (PMSF); yeast extract–peptone–sucrose (YEP-Suc); yeast extract–peptone–glucose (YEP-Glu); yeast extract–peptone–glycerol (YEP-Gly); brain heart infusion (BHI).

β-Glucosidase activity in a Saccharomyces cerevisiae wine strain

β-Glucosidase activity contributes to aroma formation during the winemaking process. This study investigated whether β-glucosidase activity was expressed by wild Saccharomyces cerevisiae strains and by a laboratory strain. β-Glucosidase activity was assayed on several culture media and under various growth conditions. The highest activities were obtained in Yeast Extract Peptone medium, but activity was also detected using grape juice as the growth medium, although a 25% drop activity was observed when anaerobic conditions were employed. A number of parameters affecting β-glucosidase activity were evaluated. Optimal conditions for activity were pH 4 and a temperature of 40–50 °C. The results showed β-glucosidase activity to be present during the process of winemaking, although different from the optimal conditions.

Yeast V-ATPase Complexes Containing Different Isoforms of the 100-kDa a-subunit Differ in Coupling Efficiency and in VivoDissociation

The 100 kDa a-subunit of the yeast vacuolar (H(+))-ATPase (V-ATPase) is encoded by two genes, VPH1 and STV1. These genes encode unique isoforms of the a-subunit that have previously been shown to reside in different intracellular compartments in yeast. Vph1p localizes to the central vacuole, whereas Stv1p is present in some other compartment, possibly the Golgi or endosomes. To compare the properties of V-ATPases containing Vph1p or Stv1p, Stv1p was expressed at higher than normal levels in a strain disrupted in both genes, under which conditions V-ATPase complexes containing Stv1p appear in the vacuole. Complexes containing Stv1p showed lower assembly with the peripheral V(1) domain than did complexes containing Vph1p. When corrected for this lower degree of assembly, however, V-ATPase complexes containing Vph1p and Stv1p had similar kinetic properties. Both exhibited a K(m) for ATP of about 250 microm, and both showed resistance to sodium azide and vanadate and sensitivity to nanomolar concentrations of concanamycin A. Stv1p-containing complexes, however, showed a 4-5-fold lower ratio of proton transport to ATP hydrolysis than Vph1p-containing complexes. We also compared the ability of V-ATPase complexes containing Vph1p or Stv1p to undergo in vivo dissociation in response to glucose depletion. Vph1p-containing complexes present in the vacuole showed dissociation in response to glucose depletion, whereas Stv1p-containing complexes present in their normal intracellular location (Golgi/endosomes) did not. Upon overexpression of Stv1p, Stv1p-containing complexes present in the vacuole showed glucose-dependent dissociation. Blocking delivery of Vph1p-containing complexes to the vacuole in vps21Delta and vps27Delta strains caused partial inhibition of glucose-dependent dissociation. These results suggest that dissociation of the V-ATPase complex in vivo is controlled both by the cellular environment and by the 100-kDa a-subunit isoform present in the complex.

Aerobic biodegradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) as a nitrogen source by a Rhodococcus sp., strain DN22

An aerobic, Gram-positive bacterium was isolated from explosives-contaminated soil by enrichment culture, using the nitramine explosive, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), as the sole added N source. The organism, identified by 16S rDNA analysis as a Rhodococcus sp., strain DN22, grew exponentially with a mean generation time of 6.5 h at 25°C in minimal medium containing RDX as the sole N source. The growth medium was depleted of RDX 24 h after inoculation but growth did not cease until 20 h later. It was concluded that strain DN22 was using NO − 2, released from RDX, as a growth substrate because, following inoculation of strain DN22 into RDX-containing minimal medium, the concentration of NO − 2 increased during the first 10 h of incubation and declined to undetectable amounts 20 h later. The ratio of the growth yields of strain DN22 grown on RDX or NO − 3 as N sources indicated that three of the six N atoms of RDX were being incorporated into biomass. Increased concentrations of NH + 4 in the growth medium reduced the extent of RDX degradation. Nitrite was produced from RDX by resting cell suspensions grown on RDX, NO − 3, NO − 2 or glutamine as N sources, but not by cells grown on NH + 4–N or in peptone-yeast extract medium. Resting cells grown on RDX showed the highest degradative activity, compared to cells grown on alternative N sources, indicating that the RDX degradation system is inducible. When soil was inoculated with RDX-grown cells of strain DN22rr, a rifampicin-resistant derivative of strain DN22, there was significant biodegradation of RDX. The addition of oat chaff to soil stimulated the growth of strain DN22rr and enhanced biodegradation of RDX, resulting in 90% degradation of the explosive in 21 d.

Interference of peptone and tyrosine with the lignin peroxidase assay.

The N-unregulated white rot fungus Bjerkandera sp. strain BOS55 was cultured in 1 liter of peptone-yeast extract medium to produce lignin peroxidase (LiP). During the LiP assay, the oxidation of veratryl alcohol to veratraldehyde was inhibited due to tyrosine present in the peptone and the yeast extract.

Protein degradation by Prevotella intermedia and Actinomyces meyeri supports the growth of non-protein-cleaving oral bacteria in serum.

The proteolytic activities of oral bacteria are thought to play an important role in the aetiology of dental abscesses. Bacteria-derived proteases may contribute to tissue destruction, and are likely to impair host defence by degrading immunoglobulins and complement. Degraded periodontal tissue and tissue fluid are likely to constitute essential sources of nutrients in the abscess. Tissue fluid, which is derived from serum, is rich in protein and poor in carbohydrate, suggesting that breakdown of protein and fermentation of amino acids is a crucial step to generate energy for growth of the microflora. The number of oral bacterial species that perform hydrolytic cleavage of protein into polypeptides, the first step in protein degradation, is relatively small compared to the large majority of peptidase-producing species. In this study, we therefore investigated the growth-promoting effect of proteinase-producing species like Prevotella intermedia and Actinomyces meyeri on the growth of some non-proteinase producing bacteria in mixed cultures. We used serum as a substitute for the supposed natural substrate of the abscess microflora. The breakdown of serum proteins was investigated using capillary electrophoresis. Poor growth was found in mono- and mixed cultures of non-proteinase producing species Eubacterium lentum, Fusobacterium nucleatum. Peptostreptococcus micros, and Streptococcus intermedius. The presence of P. intermedia in mixed cultures strongly enhanced growth of these 4 species, according to the hypothesis that the growth of the mixed cultures was peptide-limited. The enhanced growth of P. intermedia in pronase-digested serum indicated peptide-limited growth of this organism in serum, despite its production of proteinase. We found that growth of monocultures of Actinomyces meyeri was poor. In contrast, A. meyeri grew well in mixed cultures and its presence stimulated growth of F. nucleatum and P. micros, suggesting a synergistic relationship. The growth of mono- and mixed cultures was investigated using one representative strain of each species. Thus, there is a small risk of having selected unique strains. Proteinase inhibitors reduced the growth of Porphyromonas gingivalis, Prevotella nigrescens, and P. intermedia in trypticase peptone-yeast extract medium with, and without, IgG. Our study indicated that proteinase-producing organisms play a key role in mixed cultures of oral bacteria in human serum by providing polypeptides for growth. This may explain their association with dental abscesses.

Desulfotomaculum aeronauticum sp. nov., a Sporeforming, Thiosulfate-Reducing Bacterium from Corroded Aluminium Alloy in an Aircraft

A strictly anaerobic, mesophilic, thiosulfate-reducing bacterium, that was sporeforming, rod-shaped and motile, was isolated from corroded aluminium alloy in an aircraft. H 2 /CO 2 , formate, pyruvate, glycerol, and alanine were used as electron donors and carbon sources with thiosulfate or sulfite as electron acceptor. Pyruvate was incompletely oxidized to acetate. Sulfate did not serve as an electron acceptor. Growth was observed on peptone-yeast extract medium. The optimum temperature for growth was 37 °C, the pH optimum was 7.0. Addition of sodium chloride was not necessary. Vitamins were required for growth. The G + C content of the DNA was 43.8 mol%. Comparative 16S rDNA sequence analysis revealed a relationship of the new isolate to Desulfotomaculum ruminis and D. nigrificans (sequence similarity 92.6 and 93.0%, respectively). The isolate is described as a new species, Desulfotomaculum aeronauticum . The type strain is strain 9 (= DSM 10349).

Minimum Inhibitory Concentration (MIC) of Sodium Lactate and Sodium Chloride for Spoilage Organisms and Pathogens at Different pH Values and Temperatures

A selection of food spoilage organisms and pathogens were screened for sensitivity towards sodium lactate. The effect of pH (5.7 to 7.0) and temperature (4 to 37°C) on the minimum inhibitory concentration (MIC) was determined in a peptone-yeast extract medium. NaCl was used as a reference to distinguish between the effect of water activity (aw) and the specific inhibitory effect of sodium lactate. In general, if MIC values of sodium lactate decreased at low temperature, those of NaCl decreased as well. Compared to NaCl, much lower molar concentrations of sodium lactate were needed to prevent growth. For most of the bacteria, MIC values of sodium lactate strongly decreased at low pH values. At pH 5.7, the presence of sodium lactate (≥268 mM) often did not allow growth. However, for Staphylococcus aureus, Lactococcus cremoris, Lactococcus lactis and some lactic acid bacteria isolated from spoiled meat products, the MIC value of sodium lactate did not change with pH. These organisms were relatively strongly inhibited by sodium lactate at high pH (7.0). Yeasts were less sensitive to sodium lactate than the bacteria. In most cases, MIC values of sodium lactate for Debaryomyces hansenii, Candida zeylanoides, and Zygosaccharomyces bailii exceeded the highest concentration used for screening (1,339 mM), independent of the pH of the growth medium. Rhodotorula mucilaginosa was more sensitive, the MIC value of sodium lactate being about 893 mM. MIC values of NaCl appeared to be independent of the pH in the range 5.7 to 7.0 for all microorganisms that were screened.

Role of biotic factors in the control of soil-borne fungi by fluorescent pseudomonads

Several biological agents isolated from the rhizosphere of cabbage plants were shown to be able to attack antagonistic strains of Pseudomonas fluorescens. Bdellovibrio sp. formed plaques on layers of Ps. fluorescens cultivated on a yeast extract-peptone medium; on the other hand, addition of fluorescent pseudomonads increased the population of Bdellovibrio sp. in rhizosphere soil. Non-identified protozoa and nematode species were shown to feed on Ps. fluorescens grown on artificial media.

Evidence for presence in the cell wall of Candida albicans of a protein related to the hsp70 family

We have previously reported the isolation of several clones from a cDNA expression library from Candida albicans, one of which was associated with a constitutively expressed 70-kDa protein. The moiety was present in the beta-mercaptoethanol extracts of cell walls from both blastoconidia and germ tubes. The surface expression of this moiety was revealed by an indirect immunofluorescence assay using affinity-purified antibody to the fusion protein produced by the clone. The 0.68-kb cDNA insert was sequenced. A database search revealed extensive homology with the 70-kDa family of stress or heat shock proteins (hsps). The 77% homology with another C. albicans HSP70 sequence suggested that this fragment represented a second member of the HSP70 family in this organism. Homology ranging from 65 to 76% was observed with members of four subfamilies (SSA, SSB, SSC, and SSD) of the Saccharomyces cerevisiae HSP70 gene family. The nucleic acid sequence and the deduced amino acid sequence of the open reading frame showed greatest homology with SSA1 and SSA2 sequences, and the gene corresponding to the cDNA clone was designated C. albicans SSA2. The relationship with the SSA family was supported by reactivity of the 70-kDa component with antibody recognizing the Ssa proteins of S. cerevisiae. The presence of an hsp70 in the cell wall was confirmed by two additional methods. Cell wall proteins were biotinylated with a non-membrane-permeable derivative to distinguish extracellular from cytosolic proteins. Biotinylated hsp70 was detected by Western blotting (immunoblotting) among the biotinylated components affinity purified by chromatography on streptavidin, thereby establishing its presence in the cell wall. Immunoelectron microscopy showed that the 70-kDa component was present at the cell surface as well as the outer surface of the plasma membrane and extended through the cell wall, occasionally appearing to reach the cell surface through channels. Northern (RNA) blot analysis showed that the gene was expressed in yeast cells growing in yeast extract-peptone medium at both 25 and 37 degrees C and in Lee medium at 25 degrees C and during formation of germ tubes in Lee medium 37 degrees C. No obvious increase in the expression level was detected after the temperature shift. Members of the hsp70 family have been reported to be immunoreactive. The fusion protein produced by the cDNA clone was recognized by serum from healthy individuals and patients with candidiasis. Since members of the hsp70 family of eucaryotic proteins are associated with chaperone and translocation functions, in addition to being immunogenic, this protein may play a role in the assembly and function of other cell wall proteins.