Modified Laminar Flow Biological Safety Cabinet

Tests are reported on a modified laminar flow biological safety cabinet in which the return air plenum that conducts air from the work area to the high efficiency particulate air filters is under negative pressure. Freon gas released inside the cabinet could not be detected outside by a freon gas detection method capable of detecting 10(-6) cc/s. When T3 bacteriophage was aerosolized 5 cm outside the front opening in 11 tests, no phage could be detected inside the cabinet with the motor-filter unit in operation. An average of 2.8 x 10(5) plaque-forming units (PFU)/ft(3) (ca. 0.028 m(3)) were detected with the motor-filter unit not in operation, a penetration of 0.0%. Aerosolization 5 cm inside the cabinet yielded an average of 10 PFU/ft(3) outside the cabinet with the motor-filter unit in operation and an average of 4.1 x 10(5) PFU/ft(3) with the motor-filter unit not in operation, a penetration of 0.002%. These values are the same order of effectiveness as the positive-pressure laminar flow biological safety cabinets previously tested. The advantages of the negative-pressure return plenum design include: (i) assurance that if cracks or leaks develop in the plenum it will not lead to discharge of contaminated air into the laboratory; and (ii) the price is lower due to reduced manufacturing costs.     

Containment of Microbial Aerosols in a Microbiological Safety Cabinet

A microbiological safety cabinet was evaluated to determine conditions under which microorganisms might escape. Tests were conducted under three cabinet-closure conditions, various airflow velocities, and different laboratory operations, with 10(5), 1.1 x 10(5), and 10(6) microorganisms per cubic foot of cabinet space released per min for 5 min. The data revealed that (i) escape of a human infectious dose is possible when the cabinet is used with the glove panel off; (ii) the number of organisms that escaped from the cabinet increased with a decrease in air velocity; and (iii) an increase in the number of laboratory operations resulted in an increase in the number of organisms that escaped. Thus, when the glove panel was off, the cabinet was only safe for operations that released a small number of microorganisms into the cabinet, whereas the cabinet was safe for operations of significantly greater hazard when used with the glove panel on but with the gloves unattached.     

Mass Airflow Cabinet for Control of Airborne Infection of Laboratory Rodents

A mass airflow cabinet for handling and housing of laboratory rodents has been developed and tested. The unit consists of a high-efficiency particulate air filter and uniform distribution of air at a vertical velocity of 19 cm per s. Animals are maintained without bedding in mesh-bottomed cages that rest on rollers for rotation inside the cabinet. There is an air barrier of 90 cm per s separating the cabinet air from room air. Sampling for airborne bacteria yielded an average of 0.03 colony-forming units (CFU) per ft(3) of air inside the cabinet, whereas 28.8 CFU per ft(3) was simultaneously detected outside the cabinet during housekeeping, a reduction of almost three logs. The efficiency of the air barrier was tested by aerosolization of T3 phage. When phage was aerosolized 5 cm outside the cabinet, no phage could be detected 5 cm inside when the fans were operating; with the fans off an average of 1.6 x 10(4) plaque-forming units (PFU) per ft(3) was detected in six tests. Aerosolization of phage inside the cabinet yielded an average of 9 x 10 PFU per ft(3) outside; an average of 4.1 x 10(6) PFU per ft(3) were detected with the fans not in operation, a reduction of more than four logs. In-use studies on effectiveness showed that the cabinet significantly reduced the incidence of mice originally titer-free to Reo-3 virus. Hemagglutination inhibition antibodies to Reo-3 were detected in 9/22 (42%) mice housed in a conventionally ventilated animal laboratory while no seroconversion was detected in any of 22 mice housed in the mass air flow cabinet in the same laboratory.     

Studies on the Microbiological Transformation of Steroids

Some features of the NMR spectra of 19-hydroxy- and 19-acetoxy-steroids were presented and by making use of the features an unknown product of a microbiological transformation of 17α,20α,21-trihydroxypregn-4-en-3-one was easily characterized as a 19-acetoxysteroid.     

Studies on the Microbiological Transformation of Steroids

The microbiological reduction of the 20-carbonyl group of steroids has been investigated. Candida pulcherrima IFO 0964 and Sporotrichum gougeroti IFO 5982 converted the following substrates into the corresponding 20β-hydroxy derivatives (yields of the products are indicated in parentheses): Reichstein’s Compound S (60~70%) and 17α,21-dihydroxypregna-l,4-diene- 3,20-dione (40~80%). Rhodotorula glutinis IFO 0395 converted the following substrates into the corresponding 20α-hydroxy derivatives: Reichstein’s Compound S (65%), 17 α,21-dihydroxy- pregna-l,4-diene-3,20-dione (80%), llβ,l7α-dihydroxypregn-4-ene-3,20-dione (45%) and 17α, 19,21 -trihydroxypregn-4-ene-3,20-dione (10%).     

Studies on the Microbiological Transformation of Steroids

An attempt was made to clarify how Pellicularia filamentosa f. sp. microsclerotia IFO 6298 capable of hydroxylating C₂₁-steroids at the C-19 position converts C₁₉-steroids, especially monohydroxyderivatives of androst-4-ene-3, 17-dione. Such substrates as 11β-hydroxyandrost-4-ene-3,17-dione (I), androst-4-ene-3, 11, 17-trione (II), androsta-1,4-diene-3, 17-dione (III), 11β-hydroxyandrosta-1,4-diene-3,17-dione (IV), 14α-hydroxyandrost-4-ene-3, 17-dione (V), 15α-hydroxyandrost-4-ene-3, 17-dione (VI) and 9α-hydroxyandrost-4-ene-3, 17-dione (VII) were converted by the organism. All the main and several minor products were then isolated and identified. As a result it is concluded that this organism converts I and II into 14α-hydroxyandrost-4-ene-3,11,17-trione, III and IV into 14α-hydroxyandrosta-1,4-diene-3,1l,17-trione, V into 11α 14α dihydroxyandrost-4-ene-3, 17-dione (main) and 11β, 14α-dihydroxyandrost-4-ene-3, 17-dione (minor, a tentative structure), VI into 11β, 15α-dihydroxyandrost-4-ene-3,17-dione (main) and 15α-hydroxyandrost-4-ene-3,11,17-trione (minor, a tentative structure) and VII into 9α, 14α-dihydroxyandrost-4-ene-3, 17-dione (main) and 6β, 9α-dihydroxyandrost-4-ene-3,17-dione (minor).

In addition, the structural requirement of substrate for the 19-hydroxylation catalyzed by the organism and the influence of a hydroxyl group on steroid nucleus upon the 11β- and 14α-hydroxylations and the 11β-OH-dehydrogenation was discussed.     

Preliminary Microbiological Studies on the Preservation of Palm Wine

Palm wine is essentially a heavy suspension of yeasts and bacteria in fermenting palm sap. The water extract of a local preservative, from the bark of Sacoglottis gabonensis , failed to inhibit several yeasts and bacteria from palm wine. Sodium metabisulphite, diethylpyrocarbonate (DEPC) and sorbic acid inhibited to varying extents micro-organisms in palm wine. Sorbic acid was thought to be the most suitable preservative tested since DEPC left a residual pungent smell and sodium metabisulphite was not suitable because it is unacceptable to man above 0.35 mg/kg of body weight (Mossel, 1971). Pasteurization at 70° for 30 min was more effective than any of the chemical methods in reducing the microbial load of the wine. It is suggested that pasteurization at 70° for 30 min combined with subsequent treatment with sorbic acid may prove useful as a means of preserving palm wine.     

Microbiological Studies of Phytopathogenic Bacteria

During investigations on the catabolism of carbohydrate by the bacteria of the genus Erwinia, it was found that a large amount of 2-ketogluconic acid was aerobically produced from glucose by several strains of the Erwinia amylovora group of bacteria, while no production of 5-ketogluconic acid was ascertained in their growing cultures.     

Microbiological Studies of Coli-aerogenes Bacteria

α-Ketoglutarate was formed from the various carbohydrates including lactose, maltose, sucrose, d-glucose, d-fructose, d-galactose, d-mannose, d-mannitol, l-rhamnose, d-xylose, l-arabinose and glycerin. The influence of pH of the reaction mixture were tested, and inorganic phosphate was observed to be indispensable for α-ketoglutarate-fermentation. A cell of E. coli grown statically on glucose was found to reveal an ability of producing α-ketoglutarate under aerobic conditions. Optically dextro lactic acid was potent in the formation of a-ketoglutaric acid. The following reagents revealed the inhibiting effect on α-ketoglutarate-fermentation; CuSO₄, AgNO₃, iodoacetate, 2, 4-dinitrophenol, NaN₃, 3-sulfanilamido-6-methoxypyridazine and arsenite, while, kanamycin and 8-azaguanine has no inhibiting effect. When E. coli was grown in a glucose-medium, a small supply of air increased the yield of acetate against decreasing α-ketoglutarate.     

Microbiological Studies of Coli-aerogenes Bacteria

During investigations on the metabolisms of glucose by coli-aerogenes bacteria, it was found that the bacteria accumulated a large amount of α-ketoglutaric acid under aerobic conditions such as shaking culture, while lactic acid was ascertained to be produced anaerobically by the bacteria as was already known.     

Microbiological Studies of Coli-aerogenes Bacteria

The presence of glucose-6-phosphate markedly stimulated the anaerobic utilization of glyoxylate by either cell-free extracts or partially purified enzyme preparations of coli-aerogenes bacteria. The enzymic reduction of glyoxylate to glycollate was found to occur in the presence of TPN with the following substrates; glucose-6-phosphate, glucose plus ATP, gluconate plus ATP, glucose-1-phosphate or malate. The data indicated that the reduction of glyoxylate to glycollate was coupled to the oxidation of glucose-6-phosphate via the hexose monophosphate shunt pathway. It was propounded that the operation of the hexose monophosphate oxidative pathway might be controlled by TPN-linked glyoxylic reductase, and the mechanisms of enzymic regulation in microbial respiration were also discussed.     

Microbiological Studies of Coli-aerogenes Bacteria

α-Ketoglutarate was obtained in a very small amount by the oxidative fermentation of acetate with either a growing culture or the washed cells of Escherichia coli. This microorganism was also observed to accumulate a considerable amount of α-ketoglutarate as the oxidation-product of C₄-dicarboxylic acids such as succinate, fumarate, malate and oxalacetate. The addition of acetate to the reaction mixtures containing either C₃- or C₄-acids brought about an increase in the yield of α-ketoglutarate. The bacteria of coli-aerogenes revealed an ability of oxidizing tricarboxylic acids under suitable conditions, but there was no noticeable production of α-ketoglutarate. The formation of glyoxylate was observed to occur during the degradation of citrate by the bacteria of coli-aerogenes. Finally, a cyclic mechanism of aerobic carbon-metabolism in the bacteria was propounded and discussed.     

噬藻体的分子生物学研究进展

噬藻体是一种侵染原核藻类的病毒,可能是控制蓝藻水华生消的重要生态因子,在自然水体中大量存在.随着分子生物学和遗传学技术的不断发展,噬藻体的不断分离和发现,水生生态系统的研究内容更加丰富.对近年来国内外有关噬藻体分子生物学、遗传标记和分子生物学检测等方面的最新研究进展作了综述,并对今后研究工作进行了展望.     

Microbiological Studies on a New Species of Oospora,Oospora astringenes nov. sp.

Investigation was made on the mycological properties of a species of Oospora which was isolated from the air of bronchial asthma patient’s room, Tokyo, Japan.

This species was considered to be a new one and named as Oospora astringenes nov. sp. On the malt extract glucose agar at room temperature, the colonies appear velvety, powdery and white. Conidia are ellipsoidal or cylindrical, mostly 7.0×4.3 µ in size, hyaline.

This new species utilizes only organic compounds as a sole source of nitrogen and its growth is markedly stimulated by the addition of some vitamins.     

Studies on the Phenylphenol Derivatives with Biological Activity

More than ninety phenylphenol derivatives were tested for fungistatic activity toward ten species of agriculturally important fungi. One of N-methylcarbamates and some nitro- or chloro-substituted derivatives were highly toxic against Piricularia oryzae. From the relationship between the chemical structure and the activity, it is supposed that the reactivity, the permeability, the steric effect and the metabolic activation of the compound are the responsible factors for the fungistatic activity.     

Studies on the Phenylphenol Derivatives with Biological Activity

A number of compounds structurally related to phenylphenols were systematically synthesized as herbicides. Some of nitro-substituted derivatives show strong activity in pre-emergence test. The herbicidai activity of this series appears to relate with the pK-value of the compound.

Herbicidai activities of chloro-substituted phenylphenols were investigated. The derivatives of o-phenylpbenol and p-phenylphenol exhibited different selective toxicity between radish and rice, the latter appeared to have a specific inhibitory activity against the root growth of rice. As an attempt to analyze the correlation of herbicidai activity and chemical structure, the dissociation constant and the substituent constant π were applied in this investigation. The herbicidai activity correlated linearly with pK-value.     

漆树生物学的研究进展

从生物学方面概述了最近20多年来对漆树研究的主要进展,包括漆树品种和资源,形态解剖,漆汁道的发生和发育以及生漆的产生和贮存过程等,并指出了今后在漆树生物学方面的研究方向.