Facilitated diffusion of 6-deoxy-d-glucose by the oxidative yeast,Kluyveromyces lactis

The inducible glucose transport system of the yeast, Kluyveromyces lactis, was studied using the nonmetabolizeable glucose analogue, 6-deoxyglucose. The free sugar analogue is transported into glucose-grown cells via a facilitated diffusion system as determined by the nonconcentrative uptake of the sugar analogue, by the failure of energy inhibitors to reduce the rate of transport and by exchange diffusion across the membrane. Free 6-deoxyglucose is also transported into succinate-grown cells passively. Induction experiments revealed that 6-deoxyglucose serves as a gratuitous inducer for the glucose transport system in this yeast.     

Intracellular accumulation of mannosylerythritol lipids as storage materials by Candida antarctica

Summary Candida antarctica strain T-34, which was isolated as a biosurfactant producer, was found to produce organic acids and polyols extracellularly but not to produce biosurfactants, when grown on glucose or other carbohydrates as the sole carbon source. It was also observed microscopically that the strain contained oil globules within the cells. The intracellular lipids of the strain mainly consisted of triglycerides and mannosylerythritol lipids (MEL). The MEL content of the cells during the culture exceeded 10% of the dry cell weight, and the pattern of variation of the MEL content was very similar to that of triglycerides. All three stock strains of C. antarctica tested also accumulated a relatively large amount of MEL from glucose. These results suggested that these strains accumulated the MEL intracellularly as one of the storage materials together with triglycerides.Offprint requests to: D. Kitamoto     

Facilitated diffusion of p-nitrophenyl-alpha-D-maltohexaoside through the outer membrane of Escherichia coli. Characterization of LamB as a specific and saturable channel for maltooligosaccharides

LamB, an outer membrane protein of Escherichia coli, is a component of the maltose-maltooligosaccharide transport system. We used p-nitrophenyl-alpha-D-maltohexaoside, a chromogenic analog of maltohexaose, and a periplasmic amylase that hydrolyzes this compound to study the LamB-mediated diffusion of p-nitrophenyl-alpha-D-maltohexaoside into the periplasm. Using this approach, we were able to characterize LamB in vivo as a saturable channel for maltooligosaccharides. Permeation through LamB follows Michaelis-Menten kinetics, with a Km of 0.13 mM and a Vmax of 3.3 nmol/min/10(9) cells. Previous studies suggested that maltose-binding protein increases the rate of maltooligosaccharide diffusion through LamB. We show here that, at least in strains that are unable to transport maltooligosaccharides into the cytoplasm, maltose-binding protein does not influence the rate of substrate diffusion. The periplasmic amylase had been previously described as being of the alpha-type. We have now purified this protein and analyzed its mode of action using chromogenic maltooligosaccharides of varying length. Analysis of the hydrolytic products revealed that the enzyme recognizes its substrate from the nonreducing that the enzyme recognizes its substrate from the nonreducing end and preferentially liberates maltohexaose, in contrast to the behavior of classical alpha-amylases that are endohydrolases. Using p-nitrophenyl-alpha-D-maltohexaoside as a substrate, we determined a Km of 3 microM and a Vmax of 0.14 mumol/min/mg of protein.     

Plate diffusion assay as a rapid method for dosimetry of mutagens.

This paper presents a method for determining mutagenic concentrations of chemicals by using an agar diffusion assay. The method is based on the linear relationship between the amount of chemical placed at the center of the dish and the radius of the mutagenic zone. A brief theoretical discussion and experimental data confirming this relationship are given. Alkylating agents and mycotoxins were used to test the system. This method can be used to follow up decreased mutagenic potencies of solutions of unstable mutagens and to follow the production of mutagenic substances throughout fermentation.     

Selective Recovery of Carbohydrates from Aqueous Solution Facilitated by a Carrier

Carbohydrate recovery is an active area of supramolecular chemistry, motivated by the biological importance of saccharides as well as the unusual challenge presented by these complex substances. The recovery of carbohydrates from aqueous media is a difficult separation problem due to the large, irregular and multivalent structure and the low solubility of carbohydrates in organic solvents. A method for the selective recovery of mono‐ and disaccharides from aqueous media has been developed. The use of different organic solvents like butanol, methyl tertiary‐butyl ether (MTBE), n‐hexane or toluene for liquid‐liquid extraction of carbohydrates was investigated. This extraction process is facilitated by a carrier, i.e., primary amines such as cyclooctylamine. The influence of different parameters (temperature, amine concentration, extraction time) on the efficiency of the extraction was studied. Recovery rates up to 40 % are possible in a one‐stage process. Selectivities range from 1.3 up to 875.4.     

Radial diffusion as a sensitive method for screening endopeptidase activity in plant extracts

The radial diffusion assay was evaluated for its usefulness as a simple, inexpensive assay for screening endopeptidase activity in vegetative plant tissues. Various substrates embedded in agar were tested with trypsin and α-chymotrypsin to select those with the greatest sensitivity for detecting proteolysis. Gelatin was the most sensitive substrate for assays and could be utilized to detect less than 1 ng of α-chymotrypsin and trypsin per 25 μl of solution. Several exopeptidases could not be detected by this method at 1000-fold higher concentrations of enzymes. Extracts of leaves of 17 genera representing 12 families were surveyed semiquantitatively for proteolytic activity. The leaves of genera of the Solanaceae, Leguminosae, Gramineae, and Compositae exhibited the highest levels of activity. Only leaves from Syringa vulgaris (Oleaceae) did not exhibit proteolytic activity with this assay. The method of radial diffusion was successfully employed for the initial concentration and purification of a proteinase from potato leaves.     

A method for the selective isolation ofMyxococcus directly from soil

A new method is described for the selective isolation of species ofMyxococcus directly from soil by dilution plating. The method involves suppression of competing microorganisms with antibiotics combined with air drying and wet heat treatment of soils. Fungi were eliminated by supplementing the plating medium with cycloheximide and nystatin. Non-sporulating bacteria were controlled by air drying soils and then heating aqueous soil dilutions for 10 min at 56°C. The predominant sporulating bacteria in soil,Streptomyces andBacillus, were suppressed by adding either tiacumicin B, ristocetin or vancomycin to the medium. Swarming ofMyxococcus colonies was controlled with a casein digest-yeast extract plating medium (CY-C10 agar). Ultrasound treatment of soil suspensions gave the highest number ofMyxococcus colonies in the soils studied, but these cultures could be recovered without ultrasound. Strains ofMyxococccus fulvus, M. xanthus, M. coralloides, M. stipitatus andM. virescens were isolated from soil using this technique. Soils examined yielded one or twoMyxococcus species per sample.     

Physico-chemical determinants of physiOlogical evolution: from protocell to the human

One of the key physiological problems of evolution is elucidation of the role of environmental inorganic factors in origin of life. A statement is substantiated that a highly significant event in evolution of life was the appearance of protocells with the K cytoplasm in K water reservoirs with their subsequent adaptation to the environment in which Na dominated. This step was accompanied by replacement of the cell envelope with the cell plasma membrane. Precursors of animals' elaborated mechanism of maintenance of the K-cytoplasm with Na-counterkation in the environment. In plants, Na remains a trace element, in animals the Na and K contents are approximately equal, but they are present in different fluid phases. In animals presence of Na+ in the external medium, K+ inside cells has become an initial pre-requisition for electrogenesis and appearance of asymmetrical cells. Electrogenesis of these cells has become a physiological pre-requisition for cell differentiation, the appearance of the nerve cell. Asymmetrical cell has provided development of absorption, digestion, excretion, respiration. Formation of the inner medium has become a prerequisite for establishment of homeostasis. Serum osmolality, sodium concentration, pH, Ca2+ are the most rigidly maintained constants in the blood serum of humans.     

Quantitative determination of ristocetin by a microbiological diffusion method

Исследовались основные факторы, влияющие на микробиологическую диффузную титрацию ристоцетина. На основе полученных результатов была разработана инструкция для рутинных определений этого антибиотика в ферментационных средах с применением Bacillus subtilis в качестве тест-микроба и спонтина в качестве стандарта. Основными условиями для получения отчетливых зон ингибиции и воспроизводимых результатов являются:

1. (1)
   Титрационная среда без прибавления глюкозы с pH 6,5 после стерилизации.     
   
   

A new method for the selective isolation of actinomycetes from soil

Summary A coal-vitamin medium was developed to isolate actinomycetes from soil, which was superior to other currently used media. It increased the number of actinomycetes and inhibited the growth of other soil bacteria. The pretreatment of soil suspension with peptone (6%) and lauryl sulfate (0.05%) at 50°C for 10 min, also greatly increased the number of actinomycetes from soil prior to incubation with new medium.     

Acetylene as a substrate in the development of primordial bacterial communities

The fermentation of atmospheric acetylene by anaerobic bacteria is proposed as the basis of a primordial heterotrophic food chain. The accumulation of fermentation products (acetaldehyde, ethanol, acetate and hydrogen) would create niches for sulfate-respiring bacteria as well as methanogens. Formation of acetylene-free environments in soils and sediments would also alter the function of nitrogenase from detoxification to nitrogen-fixation. The possibility of an acetylene-based anaerobic food chain in Jovian-type atmospheres is discussed.Mention of brandname products does not constitute an endorsement by the USGS.     

Facilitated transport of oxygen in the presence of membranes in the diffusion path.

Most of the experimental observations on facilitated transport have been done with millipore filters, and all the theoretical studies have assumed homogeneous spatial properties. In striated muscle there exist membranes that may impede the diffusion of the carrier myoglobin. In this paper a theoretical study is undertaken to analyze the transport in the presence of membranes in the diffusion path. For the numerical computations physiologically relevant values of the parameters were chosen. The numerical results indicate that the presence of membranes tends to decrease the facilitation. For the nonlinear chemical kinetics of the reaction of oxygen with the carrier, this decrement also depends on the location of the membranes. At the higher oxygen concentration side of each membrane the flow of combined oxygen is transferred to the flow of dissolved oxygen. The reverse process occurs at the lower concentration side. Jump discontinuities of the concentration of the oxygen-carrier compound at each membrane are associated with these transfers. The decrement of facilitation is due to the cumulative effect of these jump discontinuities.     

Molecular evidence for a uniform microbial community in sponges from different oceans

Sponges (class Porifera) are evolutionarily ancient metazoans that populate the tropical oceans in great abundances but also occur in temperate regions and even in freshwater. Sponges contain large numbers of bacteria that are embedded within the animal matrix. The phylogeny of these bacteria and the evolutionary age of the interaction are virtually unknown. In order to provide insights into the species richness of the microbial community of sponges, we performed a comprehensive diversity survey based on 190 sponge-derived 16S ribosomal DNA (rDNA) sequences. The sponges Aplysina aerophoba and Theonella swinhoei were chosen for construction of the bacterial 16S rDNA library because they are taxonomically distantly related and they populate nonoverlapping geographic regions. In both sponges, a uniform microbial community was discovered whose phylogenetic signature is distinctly different from that of marine plankton or marine sediments. Altogether 14 monophyletic, sponge-specific sequence clusters were identified that belong to at least seven different bacterial divisions. By definition, the sequences of each cluster are more closely related to each other than to a sequence from nonsponge sources. These monophyletic clusters comprise 70% of all publicly available sponge-derived 16S rDNA sequences, reflecting the generality of the observed phenomenon. This shared microbial fraction represents the smallest common denominator of the sponges investigated in this study. Bacteria that are exclusively found in certain host species or that occur only transiently would have been missed. A picture emerges where sponges can be viewed as highly concentrated reservoirs of so far uncultured and elusive marine microorganisms.     

Determination of cyanein by the microbiological diffusion method

Был разработан метод количественного определения цианеина в ферментационных средах и в концентратах антибиотика с помощью микробиологического метода диффузии с применением в качестве тест-микроба Saccharomyces vini Sherry V3.