A Note on the Survival of some Bacteria in Different Diluents

The best diluent for four bacterial species was 0·1% (w/v) peptone solution. Tap water containing 0·1% (w/v) sodium thiosulphate was less satisfactory but tap water, tap water treated with charcoal, quarter-strength Ringer's solution, 0·85% (w/v) sodium chloride solution and glass distilled water were all bactericidal to one or more of the test species.     

Effect of Short-Term Chilling of Rumen Contents on Viable Bacterial Numbers

Anaerobic storage of whole rumen contents at 0°C for 8 and 24 h resulted in viable colony counts which were 113 and 92%, respectively, of the colony count obtained with an unstored sample. No significant differences in the percentages of the total population capable of utilizing glucose, cellobiose, starch, or xylose occurred with storage. Numerous factors were investigated as possible explanations for the increase in bacterial numbers observed after storage for 8 h in ice. Growth and multiplication of bacteria, subsampling of rumen contents, susceptibility to oxygen, lysis of protozoa with the release of viable bacteria, and rumen sampling time did not appear to be involved. Compilation of the data from all 29 of the above experiments gave a mean value for samples stored for 8 h in ice which was 134.8% of the control (P < 0.005). The effect of storage time at 0°C indicated that a significant increase in colony count occurred after 4 h, and, based on these data, 6 h was subsequently used as the standard cold-storage period. Circumstantial evidence supported the hypothesis that storage of rumen contents for 6 h at 0°C appears to alter or to break down the material responsible for cell-to-cell or cell-to-particulate matter attachment. Addition of a surfactant to the anaerobic dilution solution significantly increased total colony count of rumen contents to an extent similar to chilling in ice for 6 h. However, an additive effect was observed when surfactant-containing anaerobic dilution solution was used with samples stored for 6 h at 0°C.     

A Note on the Determination of Alcohol in Potato Tubers

Certain samples of potato tubers have been found to containan interfering substance which is estimated as alcohol by themicro-method of Friedemann and Klass (1936) as modified by Saifi(1940).This non-alcohol material can be removed by washing the alcohol-distillatewith purified heptane. Both alcohol and the interfering non-alcohol material were shownto accumulate in potatoes held in nitrogen.     

Development of a Robust Flow Cytometric Assay for Determining Numbers of Viable Bacteria

Several fluorescent probes were evaluated as indicators of bacterial viability by flow cytometry. The probes monitor a number of biological factors that are altered during loss of viability. The factors include alterations in membrane permeability, monitored by using fluorogenic substrates and fluorescent intercalating dyes such as propidium iodide, and changes in membrane potential, monitored by using fluorescent cationic and anionic potential-sensitive probes. Of the fluorescent reagents examined, the fluorescent anionic membrane potential probe bis-(1,3-dibutylbarbituric acid)trimethine oxonol [DiBAC(inf4)(3)] proved the best candidate for use as a general robust viability marker and is a promising choice for use in high-throughput assays. With this probe, live and dead cells within a population can be identified and counted 10 min after sampling. There was a close correlation between viable counts determined by flow cytometry and by standard CFU assays for samples of untreated cells. The results indicate that flow cytometry is a sensitive analytical technique that can rapidly monitor physiological changes of individual microorganisms as a result of external perturbations. The membrane potential probe DiBAC(inf4)(3) provided a robust flow cytometric indicator for bacterial cell viability.     

A Note on the Total Viable Counts and Selective Enumeration of Anaerobic Bacteria in the Caecal Content, Soft and Hard Faeces of Rabbit

Total viable counts, proteolytic, ureolytic, cellulolytic and NH⁺₄ utilizing anaerobic bacteria in caecal contents, soft and hard faeces of rabbits were studied. No significant differences between the bacterial counts from the caecum and soft faeces were observed ( P < 0·05) but there were significant differences between the bacterial counts of the soft and hard faeces ( P < 0·01).     

Diluents Effect on Inhibiting Dissolution of Organic Electrode for Highly Reversible Li-Ion Batteries

The potential of organic electrodes in lithium-ion batteries (LIBs) is highlighted by their cost-effectiveness and natural abundance. However, the dissolution of the active material in the electrolyte is a major obstacle to their use in LIBs. Although high-concentration electrolytes (HCEs) have been proposed to address this issue, they face challenges such as high viscosity, poor wettability, and suboptimal ion conductivity. Hence, this study introduces diluted electrolytes as non-solvating electrolytes to offset the physical limitations of HCEs and suppress the dissolution of organic electrodes. When a diluted electrolyte is used, perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA)—a notable organic electrode material—demonstrates superior capacity retention and rate performance, achieving 91% of capacity retained at 1000 mA g⁻¹ over 1000 cycles. Through electrochemical and spectroscopic measurements and molecular dynamics simulations, the diluted electrolyte successfully inhibits and demonstrates the dissolution of the active material, preventing capacity loss and the detrimental shuttle effect. This study presents a promising strategy for achieving highly reversible organic electrode-based LIBs through the development of nonsolvating electrolytes.     

Occurrence of Poly-β-Hydroxybutyrate in the Azotobacteriaceae

Poly-beta-hydroxybutyrate (PHB) from various representative strains of the genera Azotobacter, Beijerinckia, and Derxia was isolated and characterized. During growth in shake culture, with glucose as a carbon and energy source, and molecular nitrogen as a nitrogen source, increase in dry weight appeared linear, and PHB formed a constant percentage of the dry weight. In a medium containing 1% (w/v) glucose, PHB declined with the onset of the stationary phase of growth; with 2% (w/v) glucose, an increase in PHB content during stationary phase was noted in the case of some strains, before a subsequent decline. The decrease in PHB as a percentage of dry cellular weight (not of total amount present in the culture) during growth of some strains with 2% as opposed to 1% (w/v) glucose may be ascribed to a greater production of capsular polysaccharide. PHB content could not be used as a taxonomic criterion. Strain differences were as great as or greater than species differences. The only strain of Beijerinckia fluminensis obtained contained PHB, but it could not be grown on the nitrogen-free medium used. Two species of the genus Azotomonas, reported to be aerobic, nonsymbiotic nitrogen-fixers, did not grow on the nitrogen-free medium used and did not produce PHB during growth with a combined nitrogen source.     

A Note on the Effect of Hydrogen Chloride on the Morphology of Bacillus subtilis Spores

Gaseous hydrogen chloride, in the presence of a minute amount of water vapour, rapidly inactivated bacterial spores. Scanning electron microscopy showed that the treatment caused spores of Bacillus subtilis to collapse. Modern theories of spore structure and resistance suggest that it is likely that hydrogen chloride inactivates and causes collapse of spores by breaking disulphide bonds in coat protein and neutralizing, by protonation, peptidoglycan carboxyl groups in the underlying cortex.     

口服双歧杆菌,酪酸梭菌活菌制剂药效作用研究

利用氨苄青霉素引起ＳＰＦ－ＢＡＬＢ／Ｃ小鼠肠道菌群失调腹泻作为模型,观察肠康平制调整扬道菌群的药效作用,并与它同类单价制剂不平制剂对该ＳＰＦ－ＢＡＬＢ／Ｃ小鼠肠道菌群失调腹泻具有治疗作用,高剂量组９１０＾６ＣＦＵ／次）的治疗效果优于低剂量组（１０＾４ＣＦＵ／次）,肠康平制剂缓解ＳＰＦ－ＢＡＬＢ／Ｃ小鼠筵菌群失调后腹泻症状的时间较单价制剂略快。     

A Cost-Effective Solution for the Reliable Determination of Cell Numbers of Microorganisms in Liquid Culture

The concentration of microorganisms in growth medium is an important parameter in microbiological research. One of the approaches to determine this parameter is based on the physical interaction of small particles with light that results in light scattering. Table-top spectrophotometers can be used to determine the scattering properties of a sample as a change in light transmission. However, a portable, reliable, and maintenance-free instrument that can be built from inexpensive parts could provide new research opportunities. In this report, we show how to build such an instrument. This instrument consists of a low power monochromatic light-emitting diode, a monolithic photodiode, and a microcontroller. We demonstrate that this instrument facilitates the precise determination of cell concentrations for the bacteria Escherichia coli and Pseudomonas aeruginosa as well as the cyanobacterium Synechocystis sp. PCC 6803 and the green alga Chlamydomonas reinhardtii.     

Evaluation of Plating Media for the Determination of Viable Microorganisms in dental Plaque

Four agar media were evaluated to determine which one might be most suitable for the determination of the predominant number of viable microorganisms in dental plaque. The highest plate counts and uniformly larger microbial colonies were consistently obtained with Brain Heart Infusion Agar.