Action of Diethylstilbestrol on Staphylococci: Further Observations on the Effect of Resting Cells

Diethylstilbestrol (DS) has been shown to be active against staphylococci and other gram-positive bacteria but not against gram-negative microorganisms. The present study extends these findings. Standardized suspensions of (14)C-labeled Staphylococcus aureus serotypes III and IV and Shigella flexneri were prepared and exposed to pharmacological concentrations of DS (1 to 20 mug/ml) under diverse environmental conditions; the cells were removed by membrane filtration and the presence of radioactive substances in release to the supernatant fraction was followed by standard radioisotopic techniques. Controls were exposed similarly to the hormone vehicle alone (buffer containing 2% ethyl alcohol). DS at bactericidal concentrations above 6 mug/ml caused significant leakage of cellular radioactivity of S. aureus labeled with (14)C-glucose and (14)C-glutamic acid within 1 to 4 hr after exposure to DS. Maximum leakage of radioactivity occurred under anaerobic conditions at 37 C. Absorption studies of (14)C-labeled DS indicated that the affinity of S. flexneri for DS is markedly less than that of S. aureus. This might be one reason for the resistance of gram-negative bacteria to DS.     

An Assessment of the Effectiveness of Straw as an Algal Inhibitor in an Upland Scottish Loch

The control of algal blooms caused by a colony of black-headed gulls in an upland loch in central Scotland was attempted using bales of barley straw. The initial evidence suggests that the release of the inhibitory substance commenced 6-10 months after placement of the bales and was sustained for at least 18 months. The moored bales provided a useful substrate for benthic invertebrates, acting as a shelter and detritus trap. Algal diversity appeared not to be affected by the bales, but the cell numbers of the main species were affected.     

Arsenite-BAL as an Inhibitor of Germination

Imbibition of light-sensitive lettuce seeds in mixed solutions of sodium arsenite and 2,3-dimercaptopropanol (BAL) inhibits light-induced germination more potently than does arsenite alone, particularly at higher temperatures. There is limited reversal of the enhanced inhibition at high BAL/arsenite ratios. The complex is also more inhibitory than arsenite after shorter periods of imbibition. Monothiol compounds do not give the increased inhibition, nor do combinations of BAL with other thiol group reagents. Greater penetrability, possibly into some internal compartment of the cell, is suggested as the cause of the enhancement. Induction of germination by gibberellic acid or low temperature is equally sensitive to arsenite-BAL. The extent of the inhibition of germination of 9 other species by arsenite-BAL is not clearly related to their light-sensitivity.     

Growth Inhibition of Staphylococci by Sodium Thiosulphate

The addition of sodium thiosulphate to a medium as neutralizer of an iodine antiseptic resulted in unexpected growth inhibition of various strains of staphylococci and micrococci. The minimum growth inhibiting concentration varied with different strains. The inhibitory effect of sodium thiosulphate was more pronounced in media with low pH values than in those with high pH values, and was diminished by the addition of Tween 80. The action was also found to depend on the concentration of l -cystine in the medium. It is suggested that the use of sodium thiosulphate be avoided in growth media designed to neutralize iodine in disinfection efficiency tests when staphylococci or micrococci are used as test organisms.     

Galactose as an Inhibitor of the Expansion of Root Cells

The inhibition of the growth of cultured tomato roots by galactoseis due to an inhibition of cell expansion. Galactose is rapidlyabsorbed during the first 8 h following application and thefull inhibitory effect on extension growth of the roots is exertedwithin the first 24 h. At a concentration of 0·05 percent or less (50 per cent inhibition occurs at 0·035per cent) the galactose is not toxic and growth continues for7 days at the partially inhibited rate. The simultaneous presenceof glucose reduces galactose uptake but significant galactoseuptake continues at sites insensitive to a high concentrationof external glucose. In presence of an appropriate level ofglucose, although galactose uptake proceeds, the growth inhibitoryeffect of the galactose is fully reversed. Galactose reduces the content in the cell walls of the -cellulosefraction and during feeding with (I-¹⁴C) galactose all the cellwall fractions become labelled. The -cellulose fraction thenyields galactose of high specific activity. Glucose inhibitsthe incorporation of carbon from galactose into the -cellulosefraction and galactose inhibits the incorporation into thisfraction of the carbon of sucrose. The hypothesis is developedthat galactose inhibits cell expansion by a disruption of cellulosesynthesis which involves a direct incorporation of the externallyapplied galactose into the a-cellulose fraction of the cellwalls.     

Lysozyme Production as an Aid for Identification of Potentially Pathogenic Strains of Staphylococci

Lysozyme production is a frequent property of potentially pathogenic staphylococci. In the present study, 1,186 strains of human origin, 85 strains of animal origin, and 156 strains of Staphylococcus albus (epidermidis) were tested. Of 1,114 coagulase-positive strains of human and animal origin, 1,098 were lysozyme-positive (98.5%). On the other hand, of 157 coagulase-negative strains which, based on further investigations, belong to the potentially pathogenic staphylococci, all were lysozyme-positive. All of the 156 strains (100%) belonging to the species S. albus (epidermidis) were lysozyme-negative. We conclude that lysozyme production is a better index of potentially pathogenic staphylococci than the measurement of free coagulase, especially in cases of strains of animal origin. It is possible that lysozyme production allows a differentiation between pathogenic and nonpathogenic coagulase-negative staphylococci.     

Myoglobin as an Inhibitor of Exopeptidases from Lactobacillus sake

The effects of myoglobin on exopeptidases of Lactobacillus sake were determined. Inhibition of the aminopeptidases increased as the myoglobin concentration increased; aminopeptidase 3 was the most affected (90% inhibition). Aminopeptidases 1, 2, and 4 showed similar inhibition levels (around 60%). Myoglobin did not affect tripeptidase activity. Thus, myoglobin could limit amino acid generation in meat systems.     

影响葡萄球菌体外药敏活性的因素探讨

目的 探讨临床分离葡萄球菌耐药率的相关因素，指导临床用药。方法 对玉溪市人民医院1999～2003年临床分离1272株葡萄球菌的耐药率作回顾性分析。结果 临床分离葡萄球菌对多数药敏试验的耐药率有日渐上升趋势，且可因标本来源、培养环境、种群结构、产酶与否等因素有所差异。耐甲氧西林葡萄球菌（MRS）高于甲氧西林敏感葡萄球菌（MSS）；β-内酰胺酶阳性菌高于β-内酰胺酶阴性菌；凝固酶阴性菌高于凝固酶阳性菌；尿菌高于其他标本分离菌。结论 影响葡萄球菌耐药性的因素是多方面的；加强对葡萄球菌耐药性的监测和用药个体化是抗葡萄球菌感染策略的两个基本原则。     

The Angiosperm Gibberellin-GID1-DELLA Growth Regulatory Mechanism: How an “Inhibitor of an Inhibitor” Enables Flexible Response to Fluctuating Environments

The phytohormone gibberellin (GA) has long been known to regulate the growth, development, and life cycle progression of flowering plants. However, the molecular GA-GID1-DELLA mechanism that enables plants to respond to GA has only recently been discovered. In addition, studies published in the last few years have highlighted previously unsuspected roles for the GA-GID1-DELLA mechanism in regulating growth response to environmental variables. Here, we review these advances within a general plant biology context and speculate on the answers to some remaining questions. We also discuss the hypothesis that the GA-GID1-DELLA mechanism enables flowering plants to maintain transient growth arrest, giving them the flexibility to survive periods of adversity.     

Evaluation of Reagent-Impregnated Coagulase-Mannitol Test Strip for Speciation of Staphylococci

A new coagulase-mannitol reagent-impregnated strip test has been evaluated with 322 Micrococcaceae. Mannitol fermentation was determined accurately by this test; however, the coagulase reaction was difficult to interpret and was subject to significant error.     

Aggregation Factor as an Inhibitor of Bacterial Binding to Gut Mucosa

Modern research in the area of probiotics is largely devoted to discovering factors that promote the adherence of probiotic candidates to host mucosal surfaces. The aim of the present study was to test the role of aggregation factor (AggL) and mucin-binding protein (MbpL) from Lactococcus sp. in adhesion to gastrointestinal mucosa. In vitro, ex vivo, and in vivo experiments in rats were used to assess the adhesive potential of these two proteins expressed in heterologous host Lactobacillus salivarius BGHO1. Although there was no influence of MbpL protein expression on BGHO1 adhesion to gut mucosa, expression of AggL had a negative effect on BGHO1 binding to ileal and colonic rat mucosa, as well as to human HT29-MTX cells and porcine gastric mucin in vitro. Because AggL did not decrease the adhesion of bacteria to intestinal fragments in ex vivo tests, where peristaltic simulation conditions were missing, we propose that intestinal motility could be a crucial force for eliminating aggregation-factor-bearing bacteria. Bacterial strains expressing aggregation factor could facilitate the removal of pathogens through the coaggregation mechanism, thus balancing gut microbial ecosystems in people affected by intestinal bacteria overgrowth.