Regulation of formation of aerial mycelia and spores of Streptomyces viridochromogenes.

Growth of Streptomyces viridochromogenes on a solid glycerol-NH4NO3 salts medium was accompanied by the formation of aerial mycelia and spores. Adding 0.5% or more casein hydrolysate to the medium stimulated growth while completely repressing the formation of aerial mycelia and spores. This repression was temporary, as evidenced by the fact that transfer of the organisms to media not containing casein hydrolysate resulted in the appearance of aerial mycelia and spores. The effects of individual amino acids were tested. Glycine retarded growth and repressed formation of both aerial mycelia and spores. L-Aspartic acid, L-glutamic acid, and L-histidine stimulated or had little effect on growth and repressed formation of spores but not aerial mycelia. Repression by casein hydrolysate could not be attributed to the carbon/nitrogen ratio or the pH of the medium. Adding 1.25 to 2.5 mM adenine to the medium caused a reversal of the casein hydrolysate repression of aerial mycelium formation but did not reverse repression of sporulation. Dimethyladenine and 8-azaguanine had an effect similar to that of adenine, but a variety of other purine or pyrimidine derivatives had no effect on casein hydrolysate repression. The repression of aerial mycelium and spore formation by casein hydrolysate occurred only in media containing 15 mM or more phosphate. Aerial mycelia and spores were formed in media containing casein hydrolysate and 3 mM or less phosphate.     

Development and experimental study of a dried nutrient medium for the microbiological diagnosis of streptococcal infections

The comparative study of different protein bases has shown that the combined base containing animal blood hydrolysate (amino peptide) and acidic casein hydrolysate, moderately cleaved, in the proportion 1:1 is a good source of nitrogen and ensures the intensive growth of streptococci. As determined by the study of the physiological parameters and growth of streptococci, the presence of fodder yeast extract, glutamine, glucose and phosphates in media containing blood hydrolysate and casein hydrolysate has been found to render a stimulating effect on the growth and multiplication of these organisms. The data thus obtained have been used as the basis for developing the formula of a dried culture medium, capable of ensuring the growth of streptococci without blood or serum added and not inferior in its quality to Todd-Hewitt Broth manufactured by Oxoid Ltd. (Great Britain) and Difco Laboratories (USA). The physico-chemical and physiological characteristics of the proposed medium have been determined. The use of the new dried culture medium in medical practice will make it possible to improve the microbiological diagnosis of streptococcal infections.     

Effect of Yeast Extract Concentration on Viability and Cell Distortion in Rhizobium spp.

A low concentration of yeast extract (0·1%) in liquid media favoured rapid growth and high percentage of viable cells in cultures of Rhizobium japonicum (CB 1809), R. lupini (WU 425), R. meliloti (SU 47), R. trifolii (TA1) and a cowpea strain (CB 756). Concentrations of yeast extract > 0·35% depressed viability and produced distorted cells in all strains except SU 47: TA1 was especially sensitive. When used at 0·5–1% (w/v), each yeast extract (Difco, Oxoid, Vegemite) or casein hydrolysate produced greatly enlarged abnormal cells of TA1, each containing several granules of poly-β-hydroxybutyrate and whorls of intracytoplasmic membranes, and showing greater internal disorganisation than that seen in root nodule bacteroids. Lysogenic and non-lysogenic cultures of R. trifolii were all sensitive to yeast extract, and such sensitivity, for strains of several species, was unrelated to effectiveness in nodulating host plants. Glycine inhibited growth of all strains tested. Several other amino acids occurring in casein hydrolysate inhibited TA1 strongly and induced formation of distorted cells and spheroplasts; this distortion was partly counteracted by adding salts of calcium or magnesium. In media with 0·1% yeast extract the use of mannitol, sucrose, lactose or galactose as alternative carbon sources, each at a concentration of 0·02–1%, did not affect numbers of viable rhizobia or cell shape in all strains tested.     

Angiostrongylus costaricensis: culture of third-stage larvae to young adults in a defined medium

The third-stage larvae of Angiostrongylus costaricensis were successfully cultured to young adults in a chemically defined medium. The most suitable medium for the development was Waymouth's medium among eight defined media examined. Twenty-eight days after cultivation in this medium, 77% of the larvae developed to young adults, although these worms gradually died thereafter. When Waymouth's medium was supplemented with mouse red blood cells, these young adult worms continued their development. The mean body lengths of the worms cultivated in Waymouth's medium supplemented with RBCs were significantly larger than those of the worms in the medium without RBCs on Days 14 and 21 after cultivation. Addition of RBCs was essential for their further development. At 28 days after cultivation, the maximum body length of the worms was 2.1 mm for males and 3.3 mm for females. Additions of serum, yeast extract lactalbumin hydrolysate, and growth factors to Waymouth's medium did not provide any additional benefits for worm development.     

影响杜仲悬浮细胞生产桃叶珊瑚甙因素的研究

研究了外源激素2,4-D、NAA、6-BA、KT的不同组合以及营养添加物水解酪蛋白、酵母提取物对杜仲悬浮细胞生产桃叶珊瑚甙的影响。结果表明,在2.0mg/L2,4-D的培养基中分别添加1.0mg/LNAA、0.5mg/L6-BA、0.5mg/LKT可提高桃叶珊瑚甙含量;在培养基中添加水解酪蛋白和酵母提取物均能促进桃叶珊瑚甙的合成,以添加100mg/L水解酪蛋白和15mg/L酵母提取物时其含量最大。初步得出桃叶珊瑚甙合成的最适培养条件为添加2.0mg/L2,4-D+1.0mg/LNAA+0.5mg/L6-BA+0.5mg/LKT+100mg/L水解酪蛋白+15mg/L酵母提取物的MS培养基。     

Production and characteristics of hemolysins of Escherichia coli

Snyder, Irvin S. (University of Iowa, Iowa City), and Nancy A. Koch. Production and characteristics of hemolysins of Escherichia coli. J. Bacteriol. 91:763-767. 1996.-Filterable and nonfilterable hemolysins were produced by Escherichia coli in beef-heart infusion, casein hydrolysate, and chemically defined media. Differences were found among the three media in the time of appearance and in the relationship between production of these two hemolysins. The nonfilterable hemolysin produced in the three media, as well as the filterable hemolysin produced in the beef-heart infusion medium, were destroyed in 1 hr at 56 C. The filterable hemolysin produced in the casein hydrolysate and chemically defined media was unaffected by exposure to 56 C for 1 hr. Formalin inactivated the hemolysins produced in all three media. The optimal pH for activity of the nonfilterable hemolysin varied with time of production, whereas the optimal pH for the filterable hemolysin was constant. Certain carbohydrates were required for the production of filterable hemolysin by E. coli grown in casein hydrolysate and chemically defined media.     

拉萨河流域洪积扇不同植被类型土壤化学计量特征

洪积扇是拉萨河流域珍贵的土地资源,而明悉其土壤养分状况是对其进行科学合理开发利用的基础。为此,在拉萨河流域选取了10个洪积扇,于2020年7-8月调查了其上的植物群落组成并采集对应土壤,测定了土壤有机碳（SOC）、全氮（TN）、全磷（TP）、全钾（TK）、碱解氮（AN）、速效磷（AP）和速效钾（AK）的含量并计算其化学计量比。结果表明：10个洪积扇的60个样方中共发现植物种87种,分属于29科79属,其中禾本科和菊科的物种居多;洪积扇SOC、TN、TP、AN和AK的平均含量分别为34.38 g/kg、2.77 g/kg、0.39 g/kg、130.78 mg/kg和189.79 mg/kg,均表现为草地>灌丛>农田,其中SOC、TN、AN和AP含量在草地和农田下差异显著（P<0.05）;土壤TK的平均含量为19.68 g/kg,表现为农田>草地>灌丛;土壤AP的平均含量为3.36 mg/kg,表现为农田>灌丛>草地;土壤C：N的均值为12.75,表现为农田>灌丛>草地;土壤C：P、N：P和N：K的均值分别为102.50、8.10和0.16,均表现为草地>灌丛>农田,总体来说洪积扇土壤P元素较为稀缺;土壤N：K与SOC、TN、TP、TK、AN、AP、AK均极显著相关（P<0.01）,SOC和TN与植物群落盖度极显著正相关（P<0.01）;典范对应分析（CCA）进一步表明土壤养分及其计量比对洪积扇植物群落组成影响显著（P=0.002）,且TP、K：P和AP是影响洪积扇植物群落组成的主要土壤生态化学计量因子。综上所述,拉萨河流域洪积扇植物种相对丰富,但分布不均匀,组成不稳定。SOC、TN、TK含量相对较高但C：N值低,表现为有机质矿化速率高而土壤肥力低下;土壤TP和AP的含量均较低,洪积扇植物群落在生长发育过程中受到土壤P元素的限制。此外,研究还发现土壤N：K同C：N：P一样可作为评价土壤养分状况的生态化学计量指标。     

桂西北喀斯特峰丛洼地不同植被演替阶段的土壤脲酶活性

以桂西北喀斯特峰丛洼地不同演替阶段植被群落为研究对象,采用空间代替时间序列的方法,选取立地条件基本相似的草地、乔灌林和次生林3种次生演替植被,并以原生林为对照,通过野外调查取样和室内分析,探讨植被不同演替阶段土壤脲酶活性的变化特征及其与土壤理化性质的关系。结果发现,(1)不同植被演替阶段的土壤脲酶活性存在显著差异,草地最高(0.462 mg · g^-1 · d^-1),次生林次之(0.410 mg · g^-1 · d^-1),灌木林再次(0.371 mg · g^-1 · d^-1),原生林最低(0.194 mg · g^-1 · d^-1);(2)在喀斯特区域,土壤脲酶活性与全钾、粘粒含量、容重、碳氮比(C/N)、碱解氮占全氮的比例(AN/TN)呈正相关(P<0.01),与其他指标,如有机碳、全氮、碱解氮、微生物碳、微生物氮等均呈极显著负相关(P<0.01);(3)与脲酶活性关系密切的理化性质有全氮、碱解氮、微生物量、粘粒含量及C/N、AN/TN等。并不是所有区域的土壤脲酶活性都与SOC、TN、AN、微生物量呈正相关,当土壤养分较高,即土壤中的氮量不再是作物生长的限制因子时,脲酶活性有可能与之呈负相关。     

种植方式和裸岩率对喀斯特洼地土壤养分空间分异特征的影响

选取桂西北典型喀斯特洼地，研究了种植方式和裸岩率对土壤养分空间分布的影响.结果表明:种植方式对土壤有机碳(SOC)、全氮(TN)、全磷(TP)、全钾(TK)、碱解氮(AN)、速效磷(AP)、速效钾(AK)和C/N有显著影响；裸岩率对SOC、TN、TP、TK、AN、AK和C/N有显著影响，对SOC、TN、TP和AN的影响程度大于种植制度的影响，这主要与农户在裸岩率较低的地段耕作强度较大有关；木豆 板栗地的SOC、TN、TP、TK、AN、AK等含量显著高于其它种植方式，说明退耕在一定程度上有利于土壤养分的积累；受地形地貌特征和土地利用结构的影响，SOC的空间分布表现为坡脚大于洼地;AP的空间分布与SOC不同，主要受施肥影响，表现为洼地高于坡脚.     

Oesophagostomum radiatum: Glucose metabolism of larvae grown in vitro and adults grown in vivo

Larval stages of Oesophagostomum radiatum grown in vitro and adults grown in vivo were incubated in complex media or in a simple salt solution containing radioactive glucose. Glucose disappearance and end product accumulation of third-stage larvae in a simple salt solution indicated that they excreted CO₂ and acetic, propionic, and lactic acids. Larvae in third molt, fourth stage, and adults all excreted CO₂, acetic, propionic, and lactic acids at twice the rate of third-stage larvae plus an additional product, methylbutyric acid. Carbon dioxide arose primarily from the 3 or 4 carbons of glucose. An anaerobic atmosphere (95% N₂:5% CO₂) had no apparent effect on metabolism. When incubation was done in complex media, isobutyric and 3-methylbutyric acids were seen as major excretion products (10 and 24%, respectively). However, these acids were quantitatively minor when incubations took place in simple salts-glucose medium (1 and 0–3%, respectively).     

县域农田土壤氮素空间分布特征及其影响因素

采用地统计学与GIS相结合的方法,研究了四川省双流县土壤氮素空间分布特征及其影响因素.结果表明：土壤全氮和碱解氮含量具有中等空间相关性,其空间相关距离分别为15480 m和26980 m.土壤全氮含量高值区主要位于北边的九江、新兴两镇,低值区主要位于东南方向的合江、三星两镇;土壤碱解氮含量从北向南递减趋势比较明显.灰色冲积物上发育的土壤全氮和碱解氮含量均显著或极显著高于紫色岩风化物和老冲积物;水稻土全氮和碱解氮含量均极显著高于黄壤和紫色土;地形条件对土壤全氮和碱解氮含量的影响程度不同,但均以丘陵最低;不同土地利用方式下,水田全氮和碱解氮含量均显著或极显著高于旱地和果园;土壤氮素高值区施肥量明显高于低值区.     

Infectivity of Pratylenchus penetrans on Alfalfa

The infectivity of Pratylenchus penetrans on alfalfa seedlings cv. Du Pulls was studied. The dense root-hair zone was the preferred zone of penetration by females, males, and third-stage larvae. A lesion initially appeared as a water-soaked area at the root surface, becoming yellow and elliptical as the nematode entered the cortex, with dark-brown cells later appearing in the centre as the nematode fed. At 20 C, females penetrated roots earlier, faster, and in greater numbers than either males or third-stage larvae. Females penetrated roots at temperatures from 5 to 35 C, with maximum penetration between 10 and 30 C, while males and third-stage larvae penetrated roots only between 10 and 30 C with maximum penetration a t 20 C. Penetration of roots by females, males, and third-stage larvae increased after storage of 5 C for 35 days, but decreased after storage of 140 days or more. Combinations of the three life stages in pairs neither enhanced nor inhibited penetration of roots by individual life stages; males were not attracted to females. Increasing inoculum density up to 20 nematodes/seedling did not affect penetration.     

Onchocerca volvulus: biochemical and morphological characteristics of the surface of third- and fourth-stage larvae

The annulated cuticles of third- and fourth-stage larvae of Onchocerca volvulus have the typical structure of other nematodes but the cuticle of fourth-stage larvae was thinner. The surface of the third-stage larva was wrinkled and fuzzy, while that of the fourth-stage was smooth. Intermediate stages in the formation of the new cuticle and epicuticle beneath the old basal layer and of the separation of the cuticles are shown. Monoclonal antibodies specific to the surface of third-stage larvae did not react with the surface of the fourth-stage larvae. Binding of the monoclonal antibodies to the third-stage larvae was abrogated by treatment of the worms with trypsin and proteinase K, but was unaffected by treatment with periodate or the detergents sodium deoxycholate and SDS. The lectins RCA120 and WGA, but not any of the other lectins tested, bound only to the surface of fourth-stage larvae, and not to that of third-stage larvae. The surfaces of third- and fourth-stage larvae were shown to be different and contained stage-specific surface epitopes.     

The Inhibitory Effect of Sodium Deoxycholate on Escherichia coli

SUMMARY: Sodium deoxycholate (0.2%) inhibited growth of Escherichia coli in semi-digested meat and milk, but had very little effect in media in which the source of nitrogen was amino acids or ammonia. The addition of more digested forms of protein (peptone and casein hydrolysate) to a less digested form (beef infusion) overcame the inhibitory effect. The significance which this phenomenon may have in controlling the population of E. coli in the small intestine is discussed.     

Optimization of casein-based semisynthetic medium for growing of toxigenic Corinebacterium diphtheriae in a fermenter

Diphtheria toxin is produced by growing Corinebacterium diphtheriae either in a semisynthetic casein-based medium or in the Pope-Lingood meat extract based medium. The World Health Organization advises the use of the semisynthetic one, as it has important advantages. Data on the composition of casein-based media and their ability to support high toxin production are not freely available. Important factors affecting toxin production during C. diphtheriae cultivation are the pH of the culture medium and the concentration of casein hydrolysate and of Fe2+. We established that the optimal pH for toxin production is 7.2. The highest yield of toxin was obtained using a casein hydrolysate concentration of 35.0 g/L and a Fe2+ concentration of 0.05-0.41 microg/mL. Under these conditions, diphtheria toxin with higher purity and yield compared with the batches obtained using the meat-based medium of Pope-Lingood was produced.     

In vitro effect of larval stages of Ascaris lumbricoides on human blood clotting

The effects of larval stages of Ascaris lumbricoides on human blood clotting was studied in vitro. Extracts and excretory/secretory products of third-stage larvae (L3) and late third-stage larvae (LL3) cultured from ova obtained from infected patients were analysed for anti-coagulant activity. Prothrombin time (PT) was prolonged by the addition of either whole extract of L3/LL3 or ES products of L3/LL3 as compared to controls. Partial thromboplastin time with kaolin (PTTK) was also prolonged on the addition of either extracts of ES products of L3/LL3. The prolongation of PTTK was significantly higher with extracts/ES products of L3 when compared to the extracts/ES products of LL3 (p less than 0.005). Thrombin time (TT) was prolonged by extracts of L3/LL3 and their ES products.     

Joint effect of nitrogen sources and B vitamin supplementation of date juice on lactic acid production by Lactobacillus casei subsp. rhamnosus

The use of date juice as a substrate for lactic acid production was investigated. Various nitrogen sources were compared with yeast extract for efficient lactic acid production by Lactobacillus casei subsp. rhamnosus. Among different nitrogen sources added to date juice (yeast extract, ammonium sulfate, tryptic soy, urea, peptone, and casein hydrolysate), yeast extract was the most efficient. The effect of yeast extract could have been due to its B vitamin content. The addition of five B vitamins at less than 25 mg/l to date juice with any nitrogen source enhanced lactic acid production to some extent, except for date juice with yeast extract or urea or peptone. The most significant increase was obtained with ammonium sulfate. Half of the yeast extract content (10 g/l) in a supplemented date juice could be replaced by a mixture of B vitamins at less than 25 mg/l, and ammonium sulfate at 2.6 g/l with no significant decrease in lactic acid production.     

Life cycle of Hysterothylacium haze (Nematoda: Anisakidae: Raphidascaridinae)

Natural infections with Hysterothylacium haze in the Japanese common goby, Acanthogobius flavimanus, were observed in detail. In gobies in which no worm eggs were deposited, second-stage larvae were found in the digestive tract wall, and third-stage larvae occurred in the digestive tract wall, mesentery, and body cavity, whereas fourth-stage larvae and adults were found in the body cavity. This stage-habitat relationship demonstrates the infectivity of second-stage larvae to the goby and the larval migration. In heavily infected gobies, eggs and all worm stages, from hatched second-stage larvae to adults, often were found together in the body cavity of one individual host, suggesting that hatched second-stage larvae can develop in the body cavity. It was shown experimentally that H. haze develops to the second stage in the egg and does not hatch spontaneously. When a goby was fed the viscera of heavily infected gobies containing eggs and various stages of worms or artificially incubated eggs containing second-stage larvae, second- and third-stage larvae were recovered from the digestive tract wall, and fourth-stage larvae and adults were found in the body cavity. When polychaetes or crustaceans were placed in contact with infected goby viscera or incubated eggs, only second-stage larvae were recovered from the body cavity of the invertebrates. The experimental results were consistent with observations on natural infections and indicate that the direct life cycle of H. haze may involve invertebrates as transport hosts.     

A rapid autolytic method for the preparation of protein hydrolysate from poultry viscera

Protein hydrolysate was prepared from poultry viscera by a procedure involving autolysis for 6h at pH 2.8 and 55 degrees C followed by heat inactivation, filtration and drying. Recovery of nitrogen in the product was 87%. The process reduced the viable count of bacteria by 5-6logcfu/g. The product contained 84% protein, 6.5% ash and 8.8% moisture. Peptide analysis by gel filtration chromatography showed size in the range of 0.5-5kDa. RPHPLC exhibited the presence of hydrophilic peptides in higher concentration than that in trypsin digest of casein. Protein hydrolysate exhibited presence of all essential amino acids in comparison with reference protein except for methionine and threonine. The product possesses excellent solubility (>93%) over a pH range of 1-12. Efficacy of the product as a bacteriological media or feed supplement is discussed.