Lipases in autolysed cultures of filamentous fungi

Fifty-one fungi from different genera and strains were checked in plate to determine lipase activity in protein precipitates from their autolysed cultures. Each of them was then analysed at 3·5, 6·5 and 9·2 pH units and, as a consequence, basic lipases with high activity at 9·2 pH were found after 1 h of incubation. Only 25% of the studied fungi showed this lipase activity, among them the best producers were fungi from genus Fusarium (47% of fungi had lipase activity). In addition to lipase activity, Fusaria showed a low hydrolytic activity on cutin and suberin. The genus Aspergillus produced lipase and cutinase activity to a similar extent. Aspergillus nidulans 2544 also showed suberinase activity in a considerable amount. Penicillium species had very low activities. Other species and strains from genus Trichoderma , order Mucorales and class Basidiomycetes, did not show lipase activity in their degradative processes.     

Virulence factors and pathogenicity of Vibrio vulnificus strains isolated from seafood

The virulence factors of Vibrio vulnificus are not yet well understood. So far, many hydrolytic enzymes have been implicated in the pathogenesis of this micro-organism. The present research was carried out in order to study the presence of some of these enzymes in 133 V. vulnificus strains isolated from 45 seafood samples. The results showed that 100% of these strains were positive for the production of lecithinase and lipase (Tween-80), 99·2% for caseinolytic protease, 96·9% for DNase, 65·4% for mucinase and 46·6% for elastase. None of the strains was positive for the production of collagenase and 96% were haemolytic against sheep blood cells. In relation to colony morphology on brain heart infusion (BHI) agar and nutrient agar, 59·4% of strains showed opaque morphology on BHI agar and 57·9% on nutrient agar, 10·5% presented translucent morphology on both agars and 30·1 and 31·6% of strains showed a mixture of opaque and translucent morphology on BHI agar and nutrient agar, respectively. None of the translucent colonies was virulent to mice. Therefore, opacity was a useful marker for potential virulence. Of 45 food samples contaminated with V. vulnificus , 29 (64·4%) presented strains lethal to adult mice.     

Drought tolerance by lentil rhizobia (Rhizobium leguminosarum) from arid and semiarid areas of Pakistan

Ten strains of lentil rhizobia (Rhizobium leguminosarum ) were evaluated for drought tolerance by exposing them to soil moisture potentials of −0·03, −1·0 and −1·5 MPa. Water availability, rhizobial strain and time of exposure to drought had a significant ( P ≤ 0·001) effect on the number of surviving rhizobia g⁻¹ of soil. Highest cell counts were observed at −0·03 MPa, followed by soil maintained at −1·0 and −1·5 MPa. Five strains originating from saline areas showed significantly ( P ≤ 0·05) better survival under low water potential after 35 days. Two strains exhibited greatest survival under low water potential and produced viable cell counts of more than 10⁷ rhizobia g⁻¹ of soil. These strains could probably be used successfully as inoculants for lentil production in arid and semi-arid environments.     

Isolation and characterization of four polycyclic aromatic hydrocarbon degrading bacteria from soil near an oil refinery

Four bacterial strains (I-IV) capable of optimum growth on 0·1% naphthalene, anthracene or a mixture of naphthalene and phenanthrene were isolated from soil near an oil refinery. Two isolates (I and II) were identified as belonging to the genus Micrococcus , while strains III and IV were identified as Pseudomonas and Atcaligenes respectively. All the isolates were found to bear high molecular weight plasmid DNA (isolate I and IV 89%, II 67·5% and III 92·1% of Λ DNA), which is presumed to aid in the metabolism of polycyclic aromatic hydrocarbons. The strains also showed appreciable growth at high concentrations of NaCl (up to 7·5%).     

Selectivity in the heavy metal removal by exopolysaccharide-producing cyanobacteria

Aims:  The aim of this study was to assess the selective removal of Cu(II), Cr(III) and Ni(II) by strains of exopolysaccharide (EPS)-producing cyanobacteria, and to investigate the interaction of sorption in solutions with multiple-metals.
Methods and Results:  Nine EPS-producing cyanobacteria were tested for their ability to remove Cr, Cu and Ni in both single- and multiple-metal solutions. In the single-metal solutions, some of the strains showed very high values of metal uptake, however, only two of them showed the capability to selectively remove one or two of the metals present in the multiple-metal solutions. In multi-metal systems, the binding process was either noninteractive, synergistic or competitive between metal ions for different strains of cyanobacteria.
Conclusions:  Cyanothece 16Som 2 showed significantly greater sorptive capacity for Cu (1·5–20×) and Cr (2–50×) than all other strains tested. The Nostoc PCC 7936 strain showed high specific and almost exclusive selectivity towards Cu, which suggests its use aimed at recovering this metal from multiple-metal solutions.
Significance and Impact of the Study:  To find out microbial sorbents with good metal selectivity may be very useful for building up processes aimed to recover valuable metals from industrial wastewaters.     

Protein Profile of <Emphasis Type="Italic">Acidithiobacillus ferrooxidans</Emphasis> Strains Exhibiting Different Levels of Tolerance to Metal Sulfates

Strains of Acidithiobacillus ferrooxidans exhibited differences in the inhibition of Fe²⁺ oxidation in the presence of 250 mM of cadmium, zinc, and manganese sulfates in respirometric assays. Strains LR and I35 were practically not inhibited, whereas strains SSP and V3 showed significant inhibition (30–70%). Analysis by SDS-PAGE of total proteins from cells grown in the absence of metal sulfates showed different profiles between the more tolerant strains (LR and I35) and the more susceptible ones (SSP and V3). Total proteins of strains LR and V3 were also resolved by two-dimensional polyacrylamide gel electrophoresis (2-DE). A set of major proteins (40, 32, 22, and 20 kDa) could be identified only in the more tolerant strain LR. Our results show that protein profiles analysis could differentiate A. ferrooxidans strains that considerably differ in the tolerance to metal sulfates and present low genomic similarity as revealed by Random Amplified Polymorphic DNA (RAPD) data obtained previously in our laboratory.     

Survey of metal tolerance in moderately halophilic eubacteria.

The tolerance patterns, expressed as MICs, for 250 moderately halophilic eubacteria to 10 heavy metals were surveyed by using an agar dilution method. The moderate halophiles tested included 12 culture collection strains and fresh isolates representative of Deleya halophila (37 strains), Acinetobacter sp. (24 strains), Flavobacterium sp. (28 strains), and 149 moderately halophilic gram-positive cocci included in the genera Marinococcus, Sporosarcina, Micrococcus, and Staphylococcus. On the basis of the MICs, the collection strains showed, overall, similar responses to silver, cobalt, mercury, nickel, lead, and zinc. All were sensitive to silver, mercury, and zinc and tolerant of lead. The response to arsenate, cadmium, chromium, and copper was very heterogeneous. The metal susceptibility levels of the 238 freshly isolated strains were, in general, very heterogeneous among the four taxonomic groups as well as within the strains included in each group. The highest toxicities were found with mercury, silver, and zinc, while arsenate showed the lowest activity. All these strains were tolerant of nickel, lead, and chromium and sensitive to silver and mercury. Acinetobacter sp. strains were the most heavy-metal tolerant, with the majority of them showing tolerance of eight different metal ions. In contrast, Flavobacterium sp. strains were the most metal sensitive. The influence of salinity and yeast extract concentrations of the culture medium on the toxicity of the heavy metals tested for some representative strains was also studied. Lowering the salinity, in general, led to enhanced sensitivity to cadmium and, in some cases, to cobalt and copper. However, increasing the salinity resulted in only a slight decrease in the cadmium, copper, and nickel toxicities.(ABSTRACT TRUNCATED AT 250 WORDS)     

Survey of metal tolerance in moderately halophilic eubacteria

The tolerance patterns, expressed as MICs, for 250 moderately halophilic eubacteria to 10 heavy metals were surveyed by using an agar dilution method. The moderate halophiles tested included 12 culture collection strains and fresh isolates representative of Deleya halophila (37 strains), Acinetobacter sp. (24 strains), Flavobacterium sp. (28 strains), and 149 moderately halophilic gram-positive cocci included in the genera Marinococcus, Sporosarcina, Micrococcus, and Staphylococcus. On the basis of the MICs, the collection strains showed, overall, similar responses to silver, cobalt, mercury, nickel, lead, and zinc. All were sensitive to silver, mercury, and zinc and tolerant of lead. The response to arsenate, cadmium, chromium, and copper was very heterogeneous. The metal susceptibility levels of the 238 freshly isolated strains were, in general, very heterogeneous among the four taxonomic groups as well as within the strains included in each group. The highest toxicities were found with mercury, silver, and zinc, while arsenate showed the lowest activity. All these strains were tolerant of nickel, lead, and chromium and sensitive to silver and mercury. Acinetobacter sp. strains were the most heavy-metal tolerant, with the majority of them showing tolerance of eight different metal ions. In contrast, Flavobacterium sp. strains were the most metal sensitive. The influence of salinity and yeast extract concentrations of the culture medium on the toxicity of the heavy metals tested for some representative strains was also studied. Lowering the salinity, in general, led to enhanced sensitivity to cadmium and, in some cases, to cobalt and copper. However, increasing the salinity resulted in only a slight decrease in the cadmium, copper, and nickel toxicities.(ABSTRACT TRUNCATED AT 250 WORDS)     

A two-year study of the distribution of ''thermophilic'' campylobacters in human, environmental and food samples from the Reading area with particular reference to toxin production and heat-stable serotype

The incidence of 'thermophilic' campylobacters in foods and environmental samples has been studied over a two-year period. Of 781 environmental samples, 529 (67%) were found to contain campylobacters, and campylobacters were isolated from 835 (39%) of 2116 food samples. Sewage was almost always contaminated with campylobacters (96·6% of samples) and of the food samples both poultry (55·5%) and offal (47·0%) were commonly contaminated. Determination of the heat-stable serotypes of all strains isolated from these sources and of 921 strains isolated from human faeces showed that there was a wide distribution of serotypes in most types of sample. Serotype Pen 2 was the commonest type found in human faeces (18·9%) and it was also commonest in offal (21·3%), beef (40·0%), sewage (17·7%) and was the third commonest type in poultry. A comparison of culture media and conditions for optimal production of both cytotoxic and cytotonic enterotoxins showed that Brucella Broth incubated under microaerobic conditions for 24 h at 42°C was suitable for both toxins. Detection of cytotoxic activity was most sensitive using HeLa cells. The sensitivities of two ELISA systems and a Chinese Hamster Ovary tissue culture assay for detection of cytotonic enterotoxin were comparable. Not all strains isolated from cases of enteritis in human beings produced toxin; 23·1% produced cytotonic enterotoxin and 17·5% produced cytotoxin. There was no correlation between serotype and toxin production. The wide distribution of campylobacters, indistinguishable from those isolated from cases of enteritis in human beings, leads us to conclude that simplistic statements suggesting that one particular type of food is primarily responsible for cases of human disease should not be made.     

Application of Fluorescent Antibody for Detecting Capsular Substances in Staphylococcus aureus

A fluorescent antibody technique was developed for the determination of the capsular-type of strains of Staphylococcus aureus. It compared favourably with the method using serum-soft agar (Yoshida 1972). With the new technique, many populations of encapsulated and unencapsulated strains were investigated. Of 1421 fresh isolates of Staph. aureus , 54 were encapsulated and among these 54·8% and 48·1% were mono- and polyvalent, respectively. Capsular-type antigens A and B were found in 92·5% and 44·4% of strains respectively; capsular-types C and D were found relatively infrequently. In the other group, of unencapsulated strains, capsular-type antigen production was demonstrated in 125 out of 163 strains examined. Mono- and polyvalent capsular-types (A and B antigen producing strains) comprised 77·6% and 22·4%. respectively. In these capsular-types A and B were found in 54·4% and 62·4%, respectively: capsular-type antigen C and D producing strains were again infrequent. These results indicate that a majority of ordinary Staph . aureus strains produce capsular-type antigens although isolation of the encapsulated strains is infrequent.     

Effect of high salts concentrations on the growth of rhizobia and responses to added osmotica

Twenty-eight reference strains, 79 rhizobia isolated from Trigonella foenum graecum (fenugreek), 26 strains isolated from root nodules of Ceratonia siliqua (carob tree), 30 strains isolated from nodules of Adenocarpus decorticans and five isolated from Cytisus arboreus root nodules, were screened for their tolerance to increased concentrations of NaCl. Nine isolates of fenugreek were able to grow on medium containing 10% NaCl and one strain still grew at 14%. The effect of a range of salts at 2·5 and 5% (w/v) on the growth of rhizobia was assessed and it was shown that this effect depended on the ion form and the strains used. In general, NaCl appeared to be a good indicator of the tolerance of the strains to salts. The concentrations of the salts used were high and even at 5%, growth was not completely arrested in the less tolerant strains. Some substances, such as glutamate, proline, glycine betaine and CaCl₂, were tested as osmotica. The effect of the two amino acids and betaine was confirmed with all the strains used whereas the alleviating effect of CaCl₂ was not observed in all strains. This salt had different effects on two isolates of fenugreek. These results revealed a great diversity in salt tolerance, correlated with different responses to other stress conditions, which may be due to diversity in microbial ecology.     

Description of Bacillus thuringiensis wratislaviensis (H-47), a new serotype originating from WrocŁaw (Poland), and other soil isolates from the same area

Twenty-four Bacillus thuringienis ( Bt ) strains were isolated and examined in respect of serotype, plasmid content crystal-composing proteins and insecticidal activity. Strains PO1–PO11 and PO14–PO15 were recognized as B. thuringiensis kurstaki H3a3b3c. The strains PO12 and PO13 were found to share a common novel antigen determining the new serotype H-47, and were designated as serovar wratislaviensis . Further investigations showed that all strains carried multiple plasmids (for example six different large plasmids in PO12 strain) and formed crystals composed of either two proteins, 135·8 kDa and 66·2 kDa (strains PO1–PO11 and PO14–PO24), or on protein, 66·2 kDa (strains PO12 and PO13). Preliminary toxicity tests with crude suspensions of spores and crystals showed rather low activity (<50% mortality) against fruitfly larvae and nymphs of cockroaches and high toxic effects (up to 90% mortality) against house fly larvae.     

Auxin production by plant associated bacteria: impact on endogenous IAA content and growth of Triticum aestivum L.

Aims:  The aim of this study was to investigate the potential of bacterial strains of Bacillus, Pseudomonas, Escherichia, Micrococcus and Staphylococcus genera associated with wild herbaceous flora to enhance endogenous indole-3-acetic acid (IAA) content and growth of Triticum aestivum var. Inqalab-91.
Methods and Results:  Gas chromatography and mass spectrometric (GC–MS) analysis revealed that bacterial strains produced 0·6–8·22 μg IAA ml⁻¹ in the presence of L-tryptophan. Plant microbe experiments showed a significant positive correlation between auxin production by bacterial strains and endogenous IAA content of T. aestivum for GC–MS ( r  = 0·618; P  = 0.05) and colorimetric analysis ( r  = 0·693; P  = 0.01). Similarly, highly significant positive correlation for shoot length ( r  = 0·627; P  = 0.01) and shoot fresh weight ( r  = 0·626; P  = 0.01) was observed with auxin production under axenic conditions. Bacterial inoculations also enhanced shoot length (up to 29·16%), number of tillers (up to 97·35%), spike length (up to 25·20%) and seed weight (up to 13·70%) at final harvest.
Conclusions:  Bacterial strains have the ability to increase the endogenous IAA content and growth of T. aestivum var. Inqalab-91.
Significance and Impact of the Study:  Microbial strains of wild herbaceous flora can be effectively used to enhance the growth and yield of agronomically important crops.     

Sensitization of thermally injured spores of Bacillus stearothermophilus to sodium benzoate and potassium sorbate

The effects of sodium benzoate and potassium sorbate added to the recovery medium, at different pH values (6·5, 6·0 and 5·0), on the recovery rates and heat resistance of Bacillus stearothermophilus spores (ATCC 12980, 7953, 15951 and 15952) were investigated. Heated spores of strains 12980 and 7953 were inhibited by sorbate concentrations over 0·05%. Potassium sorbate at concentrations as low as 0·025%, and sodium benzoate at 0·1%, were very effective inhibitory agents for heat-damaged spores. Their effectiveness always increased at pH 5·0, at which no growth occurred, with sodium benzoate for strains 7953, 15951 and 15952, and with potassium sorbate for strains 15951 and 15952. Decimal reduction times, whenever recovery was possible, were not significantly ( P  > 0·05) affected. None of these compounds modified the z -values obtained for the spores of the four strains, which had a mean value of 7·53 ± 0·28.     

Susceptibility of Halobacteria to Heavy Metals

Sixty-eight halobacteria, including both culture collection strains and fresh isolates from widely differing geographical areas, were tested for susceptibility to arsenate, cadmium, chromium, cobalt, copper, lead, mercury, nickel, silver, and zinc ions by an agar dilution technique. The culture collection strains showed different susceptibilities, clustering into five groups. Halobacterium mediterranei and Halobacterium volcanii were the most metal tolerant, whereas Haloarcula californiae and Haloarcula sinaiiensis had the highest susceptibilities of the culture collection strains. Different patterns of metal susceptibility were found for all the halobacteria tested, and there was a uniform susceptibility to mercury and silver. All strains tested were multiply metal tolerant.     

Anti-Helicobacter pylori activity of Lactobacillus delbrueckii subsp. bulgaricus strains: preliminary report

Aims:  To evaluate the activities of six Lactobacillus delbrueckii subsp. bulgaricus (LB) strains against 30 Helicobacter pylori strains by agar-well diffusion method.
Methods and Results:  LB cultures [4 × 10⁸–4 × 10⁹ CFU ml⁻¹) either were prepared in milk at their native pH, 3·8–5·0, or were adjusted to pH 6·4–7·7. At low and neutralized pH, LB strains inhibited the growth by 40–86·7% and 16·7–66·7% of H. pylori strains, respectively. LB activity was strain-dependent. At low and neutralized pH, one and five H. pylori strains, respectively, were not inhibited by any LB strain. LB2 and LB3, taken together, were active against most metronidazole and clarithromycin resistant strains.
Conclusions:  All LB strains inhibited a number of H. pylori strains, including also antibiotic resistant strains. LB activity was strain-dependent and better at low pH. At low pH values, the most active LB strains were LB1, LB2 and LB3, inhibiting 86·7% of H. pylori strains, while at neutralized pH values, the most active LB strains were LB2 and LB3, inhibiting 53·3 and 66·7% of H. pylori strains, respectively.
Significance and Impact of the Study:  LB could be utilized in the treatment or prophylaxis of H. pylori infection and warrants clinical investigations.     

Assessment of cell surface properties and adhesion potential of selected probiotic strains

Aim:  To evaluate the physicochemical cell surface and adhesive properties of selected probiotic strains for human use.
Methods and Results:  Probiotic strains, Bifidobacterium longum B6, Lactobacillus acidophilus ADH, Lactobacillus paracasei , Lactobacillus rhamnosus GG, Lactobacillus brevis , Lactobacillus casei , Leuconostoc mesenteroides and Pediococcus acidilactici were tested for the physicochemical properties of cell surfaces and the adhesion abilities against foodborne pathogens. Bif .  longum B6 (53·6%) and Lact .  rhamnosus GG (46·5%) showed the highest hydrophobicity, while the least affinity to xylene was observed in Ped .  acidilactici (10·4%). Bifidobacterium longum B6 showed the strongest coaggregation phenotype with Listeria monocytogenes (53·0%), Shigella boydii (42·0%) and Staphylococcus aureus (45·9%). Lactobacillus rhamnosus GG had the strong binding ability to Caco-2 cells and effectively inhibited the adhesion of L .  monocytogenes , Salmonella Typhimurium, Sh .  boydii and Staph .  aureus to Caco-2 cells. The hydrophobicity was highly correlated with coaggregative abilities and competitive inhibition, suggesting a good relationship between in vitro adhesion and in vivo colonization.
Conclusion:  The results suggest that Bif .  longum B6 and Lact .  rhamnosus GG can be candidate probiotics available for human consumption.
Significance and Impact of the Study:  Because the use of probiotic strains has been more concerned with their beneficial effects in the GI tract, it is essential to examine the potential of probiotic strains based on the physicochemical properties in terms of bacterial-binding and adhesion capabilities.     

Large plasmids in ruminal strains of Selenomonas ruminantium

The plasmid content of six different isolates of Selenomonas ruminantium from the rumen of sheep, cows or goats was examined by electron microscopy. In addition to small plasmids (< 12 kb) studied previously, all six strains contained at least one plasmid larger than 20 kb. Plasmid sizes of 1·4, 2·1, 2·4, 5·0, 6·2, 20·4, 20·8, 22·7, 23·3, 29·3, 30·7, 34·4 and 42·6 kb were estimated from contour length measurements. DNA-DNA hybridization experiments revealed homology among the large plasmids from five strains, while the 20·8 kb plasmid from a sixth isolate showed no apparent relationship with the plasmids of the other strains.     

乌鲁木齐市道路林带土壤抗重金属细菌的筛选及重金属去除能力

【背景】道路重金属污染问题日益严峻,寻找高效的微生物资源用于环境修复已迫在眉睫。【目的】从乌鲁木齐市道路林带土壤中筛选抗重金属菌株,并对其重金属去除能力进行探究。【方法】使用含5种重金属离子(铅、镉、锌、铜、镍)的4种培养基进行抗性菌株筛选,通过形态学特征和16S rRNA基因序列进行鉴定,采用电感耦合等离子体发射光谱仪(inductively coupled plasma optical emission spectrometer,ICP-OES)检测分离株对重金属离子的去除情况。【结果】4种分离培养基中,TSA是抗重金属菌株筛选的最适培养基,共筛选出16株抗重金属菌,其中4株抗Pb菌、4株抗Cd菌、4株抗Zn菌、3株抗Cu菌和1株抗Ni菌,其抗性分别高达3 000、800、600、300和400mg/L,16株菌中以芽孢杆菌属(Bacillus)数量最多。在初始浓度为700mg/L Pb²⁺下,菌株Pb6的去除率高达92.48%,菌株Pb11、Pb3和Pb9的去除率分别为27.70%、40.37%和58.88%;在200mg/L Cd²⁺...