<Emphasis Type="Italic">In vitro</Emphasis> colonization of hydrophilic contact lenses by <Emphasis Type="Italic">Aspergillus niger</Emphasis>

In vitro colonization of hydrophilic contact lenses by Aspergillus niger was investigated. Five strains of the fungus, four polymers, two culture media and four incubation periods were considered for analysis. Only the 2700 strain colonized the lenses. The degrees of adhesion and invasion varied significantly according to the characteristics of the culture under investigation. Journal of Industrial Microbiology & Biotechnology (2002) 29, 6–9 doi:10.1038/sj.jim.7000255 Received 06 August 2001/ Accepted in revised form 23 March 2002     

Bacterial colonization of rigid gas permeable and hydrogel contact lenses by Staphylococcus aureus

Staphylococcus aureus ATCC 6538 and a clinical isolate of S. aureus from a bacterial keratitis patient were examined for their ability to adhere to etafilcon A, polymacon, silafocon, and pauflufocon A, B and C contact lenses. Both isolates adhered more to the rigid gas permeable (RGP) materials than to the hydrogel lenses tested (P < 0.05). S. aureus ATCC 6538 adhered to the etafilcon A material to a greater extent than did the clinical isolate (P < 0.05). there were no statistically significant differences in the recovery of staphylococci from unworn lens materials when surface area, composition and ionicity were evaluated for either the hydrogel or rgp lenses tested against lenses of a similar type. however, differences were observed when hydrogel lenses were evaluated against rgp lenses (P < 0.05). these differences may be related to water content. Journal of Industrial Microbiology & Biotechnology (2000) 24, 113–115. Received 12 August 1999/ Accepted in revised form 02 November 1999     

烫伤创面绿脓杆菌定植动态的实验研究

本文从细菌以多细胞生理活动观点出发,以认识定植稳定过程为目的。进行了实验大白鼠烫伤创面绿脓杆菌定植与抗定植动态观察。通过用铁浸染色法对细菌群体结构定量化研究,用糖包被负染法对群体结构内部结构观察,对粘附在组织表面细菌数量的测定,反映结构与粘附力的关系。进一步结合电镜观察及细菌生长状态的分析,证明了烫伤创面上绿脓杆菌群体结构的形成是细菌分裂繁殖所致。通过群体结构,糖包被,粘附力及生长状态的动态观察,表现出与定植的稳定程度呈平行关系,显示其重要性。联系抗定植力研究,表明定植与抗定植的一致性。最后分析了定植三个主要条件,和稳定性定植的三要素。     

Effect of the support matrix on biotransformation of benzaldehyde to benzyl alcohol by yeast cells in aqueous and aqueous-organic two phase systems

Summary Biotransformation of benzaldehyde to benzyl alcohol bySaccharomyces cerevisiae immobilized in different support matrices was investigated. Polymers with intrinsic hydrophobic and/or hydrophilic nature as well as mixed hydrophobic and hydrophilic supports were examined both in aqueous and bisphasic aqueous-organic systems. The hydrophobic support material ENTP-2000 or mixed silicone:alginate (50-2550-75) proved to be most suitable not only for nonconventional media but also for conventional aqueous media for production of benzyl alcohol. With ENTP-2000, catalytic activity and maximum yield were 159 mol h^–1 g^–1 dry weight catalyst and 0.89 mM, respectively, in hexane containing 2% moisture. Corresponding values in aqueous media were 246 mol h^–1 g^–1 dry weight catalyst and 1.53 mM. With 5050 silicone:alginate, catalytic activity and maximum yield were 177 mol h^–1 g^–1 dry weight catalyst and 1.18 mM, respectively, in hexane containing 2% moisture. Corresponding values in aqueous media were 192 mol h^–1 g^–1 dry weight catalyst and 0.8 mM.     

Bacterial adhesion measurements on soft contact lenses using a Modified Vortex Device and a Modified Robbins Device

S. marcescens 8100 andP. aeruginosa 15442 were used to study bacterial adhesion to hydrogel contact lenses which had not been worn. Bacterial removal from unworn lens materials was assessed with a calibrated vortex device modified with a digital rpm readout and fitted with a test tube attachment (MVD). The MVD, which relies on a whirlpool-like force to remove the bacteria, showed that bacteria adhered to the same degree to etafilcon A, vifilcon A and polymacon lenses under standardized conditions. Tracking the isoenzyme patterns of these bacterial species over time showed instability ofS. marcescens upon repeated passage. This instability was not evident withP. aeruginosa. Bacterial adhesion ofP. aeruginosa 15442, to human worn and unworn etafilcon A materials was determined with a Modified Robbins Device. The MRD was closed off at both ends stopping medium and bacterial movement after 1 h of fluid flow over the lens surface. The results show that immediately following this 1-h period more bacteria adhere to unworn contact lenses than to worn lenses. However, bacterial counts were equivalent on worn and unworn lenses following 5 h of static incubation.     

Evaluation of thermal disinfection procedures for hydrophilic contact lenses

The kinetics and efficacy of moist heat disinfection for hydrophilic contact lenses were investigated by using representative microorganisms of ophthalmic concern and several heat-resistant species. In replicate challenges, 80 degrees C for 10 min and 75 degrees C for 5 min were proven efficacious for moist-heat disinfection.     

Evaluation of thermal disinfection procedures for hydrophilic contact lenses.

The kinetics and efficacy of moist heat disinfection for hydrophilic contact lenses were investigated by using representative microorganisms of ophthalmic concern and several heat-resistant species. In replicate challenges, 80 degrees C for 10 min and 75 degrees C for 5 min were proven efficacious for moist-heat disinfection.     

难辨梭菌在地鼠肠粘膜中粘附定植的研究

我们对难辨梭菌(C.d.)在地鼠肠粘膜中的定植进行了细菌分离和超微结构的研究,以探索C.d.的定植及C.d.性肠炎的发病机理。结果表明,用抗生素处理再接种C.d.的地鼠肠粘膜和盲肠内容物均分离到C.d.并证明正常菌群对C.d.定植有拮抗作用。不同肠段内C.d.的定植量有较明显的差别。无毒株与毒力株定值量亦稍有不同。接种C.d.自第5天起逐渐减少。接种C.d后24小时扫描电镜可见肠粘膜粘液层内和上皮细胞表面有大量C.d.定植。透射电镜亦观察到在上皮细胞表面有C.d.定植。毒力株定植12小时可引起上皮细胞线粒体和细胞基质肿胀。     

Immobilization of yeast by adhesion to a support without use of a chemical agent

Yeast Saccharomyces cerevisiae has been immobilized by adhesion to plate supports of glass or polycarbonate after a suitable pretreatment, and sedimentation on the support, followed by washing the non-adhering cells. The pretreatment consists of starving the cells in pure water. Its efficiency is related to both a release of substances, decreasing the electrostatic repulsion between the particles involved, and a modification of the cell wall itself. A single layer of immobilized cells is obtained and a large fraction of the cells keep the capacity to reduce methylene blue and to multiply. The influence of various experimental factors (pretreatment, harvesting time, time of contact with the support) is discussed.     

Adhesion of Pseudomonas aeruginosa,Achromobacter xylosoxidans,Delftia acidovorans,Stenotrophomonas maltophilia to contact lenses under the influence of an artificial tear solution

Abstract

Corneal infection is a devastating sight-threatening complication that is associated with contact lens (CL) wear, commonly caused by Pseudomonas aeruginosa. Lately, Achromobacter xylosoxidans, Delftia acidovorans, and Stenotrophomonas maltophilia have been associated with corneal infection. This study investigated the adhesion of these emerging pathogens to CLs, under the influence of an artificial tear solution (ATS) containing a variety of components commonly found in human tears. Two different CL materials, etafilcon A and senofilcon A, either soaked in an ATS or phosphate buffered saline, were exposed to the bacteria. Bacterial adhesion was investigated using a radio-labeling technique (total counts) and plate count method (viable counts). The findings from this study revealed that in addition to P. aeruginosa, among the emerging pathogens evaluated, A. xylosoxidans showed an increased propensity for adherence to both CL materials and S. maltophilia showed lower viability. ATS influenced the viable counts more than the total counts on CLs.     

Root Colonization by Inoculated Plant Growth-Promoting Rhizobacteria

Certain rhizobacteria referred to as 'plant growth-promoting rhizobacteria' (PGPR) can contribute to the biological control of plant pathogens and improve plant growth. They enhance root development either directly by producing phytohormones, or indirectly by inhibiting pathogens through the synthesis of different compounds. PGPR are likely to be of great interest in sustainable crop protection and have drawn much attention in recent years. However, the use of these bacteria to protect crops sometimes fails because rhizobacteria are unable to recolonize the rhizosphere of inoculated plants. The colonization of roots by inoculated bacteria is an important step in the interaction between beneficial bacteria and the host plant. However, it is a complex phenomenon influenced by many biotic and abiotic parameters, some of which are now apparent. This paper summarises knowledge on rhizosphere colonization by PGPR.     

Determination of molecular associations of some hydrophobic and hydrophilic bile acids by infrared and Raman spectroscopy

The aim of this study was to analyse the Raman and infrared spectra of eight common mammalian bile acids in order to identify intermolecular interactions between hydroxyl and carbonyl groups. The results are considered in the light of the new hydrophilic/hydrophobic classification of bile acids. The alcohol OH group of the hydrophobic bile acids forms different intermolecular bonds. The most hydrophobic bile acid, lithocholic acid forms polymers, and this may explain its very low water solubility. The hydrophilic bile acids have some of their alcohol OH groups free of any intermolecular interaction. The strongly hydrophilic murideoxycholic acid also forms dimers, again consistent with a very low water solubility. The proposed structural arrangements are in agreement with published crystallographic studies. Received: 7 November 1996 / Accepted: 8 December 1996     

Invasion of a soft contact lens by Exophiala jeanselmei

The invasion of a soft contact lens by Exophiala jeanselmei is documented. All species in this genus are pathogenic. In humans E. jeanselmei is a recognized cause of mycetoma, phaeohyphomycosis and keratomycosis. This fungus has not been previously listed among lens invaders.     

Mapping of Rpb3 and Rpb5 contact sites on two large subunits, Rpb1 and Rpb2, of the RNA polymerase II from fission yeast

[Rpb1 and Rpb2] Mapping of the contact sites␣on two large subunits of the fission yeast Schizosaccharomyces pombe RNA polymerase II with two small subunits, Rpb3 and Rpb5, was carried out using the two-hybrid screening system in the budding yeast Saccharomyces cerevisiae. Rpb5 was found to interact with any fragment of Rpb1 that contained the region H, which is conserved among the subunit 1 homologues of all RNA polymerases, including the β' subunit of prokaryotic RNA polymerases. In agreement with the fact that Rpb5 is shared among all three forms of eukaryotic RNA polymerases, the region H of RNA polymerase I subunit 1 (Rpa190) was also found to interact with Rpb5. On the other hand, two-hybrid screening of Rpb2 fragments from RNA polymerase II indicated the presence of an Rpb3 contact site in the region H which is conserved among the subunit 2 homologues of all RNA polymerases, including the β subunit of prokaryotic RNA polymerases. Possible functions of the regions H in the subunits 1 and 2 are discussed. Received: 10 December 1997 / Accepted: 14 April 1998     

Colonization of North America by Drosophila subobscura: Ecological analysis of three communities of drosophilids in California

We have carried out bimonthly collections of Drosophila species during a 16 month period in three localities of California (Eureka, Davis, and Gilroy). D. subobscura, which has colonized North America only a few years ago, is well established and has an annual abundance cycle similar to that observed in the Old World. The differences between the three localities account for 26.4% of the species diversity. Davis and Gilroy exhibit similarities attributable to their similar environmental conditions. Seasonality accounts for 46% and 50.4 % of the species diversity in Davis and Gilroy respectively, but only for 39.4% in Eureka. Differences between years explain only a small percentage of the total species diversity. A correspondence analysis of the association between species and months of collection shows ecological similarities between D. subobscura and the Nearctic members of the obscura species group.     

Focal contact assembly through cytoskeletal polymerization: steady state analysis

For many cell types, initial receptor-mediated attachment to a ligand-coated surface is followed by the formation of focal contacts - strong, specialized, discrete adhesive connections between cell and substrate in which receptors are clustered and simultaneously linked to extracellular ligand and cytoskeletal proteins. Since adhesion affects many aspects of cellular physiology including growth, differentiation, and motility, understanding the biochemical factors which regulate focal contact assembly should enhance our understanding of these phenomena. In this paper, we present a mathematical model to examine how receptor-ligand, receptor-cytoskeleton, and cytoskeleton-cytoskeleton interactions affect the formation of receptor clusters which serve as precursors to mature focal contacts. Receptor clustering is presumed to occur through self-recognition of cytoskeletal elements which induce the polymerization of ligand-receptor-cytoskeleton complexes. Polymerization only occurs when the ligand density is above a critical value and a decrease in the receptor-ligand affinity shifts the critical ligand density to higher values. While cytoskeletal protein expression and receptor-cytoskeleton affinity influence the concentration of monomeric complexes, the formation of polymeric ligand-receptor-cytoskeleton aggregates is most sensitive to changes in the self-association affinity between cytoskeletal proteins. We find that a 100-fold enhancement in the affinity between cytoskeletal elements can produce a substantial increase in the total fraction of adhesion receptors associated with focal contact precursors (from 5% to over 90%). Our results suggest that under physiological conditions, cellular control of focal contact assembly most likely occurs through modulation of specific cytoskeletal proteins to solidify cytoskeleton-cytoskeleton connections within precursor focal contact structures.     

Colonization of artificial substrates by stream insects: Influence of substrate size and diversity

A field experiment was performed in a New Mexico (U.S.A.) stream to investigate the relation between size and diversity of substrate and numbers and diversity of colonizing insects. Baskets with either small gravel, large gravel, or a 1 : 1 mixture of the two sizes were placed in a riffle area and colonization was monitored for 19 days.Colonization was rapid, and both total number of individuals and number of species colonizing the substrates had stopped increasing by the end of the experiment. Fewer individuals colonized baskets downstream, suggesting that the drift is a major source of insect colonists. Small substrate supported more individuals and more species than the larger stones. Total number of individuals and the number of species on the mixed substrate were between numbers on small and large substrate. These results do not support previous generalizations on the relation between substrate size and complexity and the structure of invertebrate communities in streams. Results of the study are compared with the findings of recent experimental studies and it is suggested that earlier generalizations on the role of substrate size and complexity need to be reexamined.Order of authors was determined by the flip of a coin. Reprint requests may be sent to either author.     

Sugar utilization by yeast during fermentation

Summary When glucose and fructose are fermented separately, the uptake profiles indicate that both sugars are utilized at similar rates. However, when fermentations are conducted in media containing an equal concentration of glucose and fructose, glucose is utilized at approximately twice the rate of fructose. The preferential uptake of glucose also occurred when sucrose, which was first rapidly hydrolyzed into glucose and fructose by the action of the enzyme invertase, was employed as a substrate. Similar results were observed in the fermentation of brewer's wort and wort containing 30% sucrose and 30% glucose as adjuncts. In addition, the high levels of glucose in the wort exerted severe catabolite repression on maltose utilization in theSaccharmyces uvarum (carlsbergensis) brewing strain. Kinetic analysis of glucose and fructose uptake inSaccharomyces cerevisiae revealed aK _m of 1.6 mM for glucose and 20 mM for fructose. Thus, the yeast strain has a higher affinity for glucose than fructose. Growth on glucose or fructose had no repressible effect on the uptake of either sugar. In addition, glucose inhibited fructose uptake by 60% and likewise fructose inhibited, glucose uptake by 40%. These results indicate that glucose and fructose share the same membrane transport components.