Chemical Detection of Microbial Prey by Bacterial Predators

A motile, predacious bacterium which degraded Pythium debaryanum was strongly attracted to substances released into the medium by the fungus. A nonpredacious bacterium was not attracted to these substances. The predator bacterium was specifically attracted to cellulose and its oligomers which are known to be components of the cell wall of Pythium. Ethanol inhibited chemotaxis of the bacterium without affecting either its motility or its ability to degrade cellulose. A second predacious bacterium was isolated for the alga, Skeletonema costatum. The role of chemoreception in the detection of microbial prey by bacterial predators in natural habitats is discussed.     

Comparative study of the entomopathogenic nematode, Steinernema carpocapsae, reared on mutant and wild-type Xenorhabdus nematophila

The symbiotic interaction between Steinernema carpocapsae and Xenorhabdus nematophila was investigated by comparing the reproduction, morphology, longevity, behavior, and efficacy of the infective juvenile (IJ) from nematodes reared on mutant or wild-type bacterium. Nematodes reared on the mutant X. nematophila HGB151, in which an insertion of the bacterial gene, rpoS, eliminates the retention of the bacterium in the intestinal vesicle of the nematode, produced IJs without their symbiotic bacterium. Nematodes reared on the wild-type bacterium (HGB007) produced IJs with their symbiotic bacterium. One or the other bacterial strain injected into Galleria mellonella larvae followed by exposing the larvae to IJs that were initially symbiotic bacterium free produced progeny IJs with or without their Xenorhabdus-symbiotic bacterium. The two bacterial strains were not significantly different in their effect on IJ production, sex ratio, or IJ morphology. IJ longevity in storage was not influenced by the presence or absence of the bacterial symbiont at 5 and 15 °C, but IJs without their bacterium had greater longevity than IJs with their bacterium at 25 and 30 °C, suggesting that there was a negative cost to the nematode for maintaining the bacterial symbiont at these temperatures. IJs with or without their symbiotic bacterium were equally infectious to Spodoptera exigua larvae in laboratory and greenhouse and across a range of soil moistures, but the absence of the bacterial symbiont inhibited nematodes from producing IJ progeny within the host cadavers. In some situations, such as where no establishment of an alien entomopathogenic nematode is desired in the environment, the use of S. carpocapsae IJs without their symbiotic bacterium may be used to control some soil insect pests.     

Isolation,partial characterization and growth characteristics of a bacterium resistant to aflatoxin B1

A bacterium was isolated from the soil of dumping ground for cattle yard waste by enrichment culture containing aflatoxin B1. This bacterium was closely related to Bacillus firmus that was found to be a non-pathogenic bacterium. The minimum inhibitory concentration of aflatoxin B1 to the bacterium was found to be 80 microg ml(-1) as measured by total viable count and soluble protein content methods. The bacterium was sensitive to all the tested antibiotics. Plasmid curing by chemical agents did not show the resistance character residing in the plasmid. Protein profiles of cell extracts of aflatoxin B1 resistant bacterium grown in the presence and absence of the toxin showed 46 and 44 protein bands respectively in SDS-PAGE. It was observed that 39 bands were common in both the extracts and the remaining bands were showing differences near the high molecular weight range.     

Characterization of Rhizobium sp. Q32 Isolated from Weathered Rocks and its Role in Silicate Mineral Weathering

One mineral-solubilizing strain was isolated from weathered potassic trachyte surfaces and identified as Rhizobium sp. Q32 based on the 16S rRNA gene sequence analysis. The mineral (feldspar and biotite) dissolution potential and the physiological characteristics of the bacterium were investigated. Laboratory mineral dissolution experiments indicated that inoculation with the live bacterium significantly increased feldspar and biotite dissolution by a factor of 1.2–4.7 for Si and 1.2–1.5 for K in comparison with the dead bacterium inoculated controls. In addition, extracellular polysaccharide production by the bacterium increased with time but the bacterium produced small pH changes (6.0–6.5) in the course of mineral dissolution experiment. The bacterium was found to produce siderophores and have the characteristics of acid or alkali and salt tolerance and temperature resistance. The result suggested that feldspar and biotite dissolution may be mainly caused by extracellular polysaccharide and/or siderophores produced by the bacterium.     

Study on diversity of endophytic bacterial communities in seeds of hybrid maize and their parental lines

The seeds of plants are carriers of a variety of beneficial bacteria and pathogens. Using the non-culture methods of building 16S rDNA libraries, we investigated the endophytic bacterial communities of seeds of four hybrid maize offspring and their respective parents. The results of this study show that the hybrid offspring Yuyu 23, Zhengdan958, Jingdan 28 and Jingyu 11 had 3, 33, 38 and 2 OTUs of bacteria, respectively. The parents Ye 478, Chang 7-2, Zheng 58, Jing 24 and Jing 89 had 12, 36, 6, 12 and 2 OTUs, respectively. In the hybrid Yuyu 23, the dominant bacterium Pantoea (73.38?%) was detected in its female parent Ye 478, and the second dominant bacterium of Sphingomonas (26.62?%) was detected in both its female (Ye 478) and male (Chang 7-2) parent. In the hybrid Zhengdan 958, the first dominant bacterium Stenotrophomonas (41.67?%) was detected in both the female (Zheng 58) and male (Chang 7-2) parent. The second dominant bacterium Acinetobacter (9.26?%) was also the second dominant bacterium of its male parent. In the hybrid Jingdan 28, the second dominant bacterium Pseudomonas (12.78?%) was also the second dominant bacterium of its female parent, and its third dominant bacterium Sphingomonas (9.90?%) was the second dominant bacterium of its male parent and detected in its female parent. In the hybrid Jingyu 11, the first dominant bacterium Leclercia (73.85?%) was the third dominant bacterium of its male parent, and the second dominant bacterium Enterobacter (26.15?%) was detected in its male parent. As far as we know, this was the first research reported in China on the diversity of the endophytic bacterial communities of the seeds of various maize hybrids with different genotypes.     

利用光合菌发酵对玉米秸杆进行转化的研究*

系统研究了光合菌在氨法处理和非氨处理两种环境下,在厌氧、好氧、以及自然条件下对玉米秸秆的转化。通过发酵液中还原糖与蛋白质浓度的测定结果的比较、判断、优选出一种最适合条件下光合菌对玉米转化的途径。研究表明,在以氨化法处理的玉米秸秆为底物与光合菌的发酵实验中,发酵液中的还原糖和蛋白质的尝试都要比非氨法条件下玉米秸秆为底物与光合菌发酵实验中的发酵液中的不原糖和蛋白质的浓度高。实验结果证明了转化产生的还原糖、蛋白质都是光合菌能利用的营养成分,由此达到利用光合菌转化玉米秸秆的研究目的。     

降解菌HN36对二氯喹啉酸胁迫下烟草茎尖和叶片超微结构的影响

利用降解菌HN36降解土壤中的二氯喹啉酸及修复土壤的生态环境, 为稻田植烟地区烟叶安全生产提供技术和理论依据。采用盆栽试验, 将二氯喹啉酸与降解菌HN36配成一定量的溶液, 均匀喷洒到过筛的干土中, 将5叶期烟苗移栽到处理的塑料盆土中。当烟苗长到8叶期时分别取茎尖﹑顶叶和中部叶进行处理, 在电镜下观察细胞超微结构变化, 利用高效液相色谱仪检测土壤中二氯喹啉酸降解的动态。烟株细胞超微结构变化的程度有差异, 表现为受害烟株>修复烟株>健康烟株; 烟株的茎尖和顶叶细胞伤害最严重, 中部叶片细胞伤害较轻。研究结果还显示, 在含二氯喹啉酸的土壤中, 加入降解菌HN36能加速二氯喹啉酸降解, 改善土壤健康质量, 烟株细胞超微结构及烟叶品质明显得到修复。     

家白蚁中肠具有内切葡聚糖酶活性菌株的分离和鉴定

从家白蚁中肠分离得到了一株具有内切β-1,4-葡聚糖酶活性的细菌Streptomyces sp.Cf1,并经过16S rRNA和形态分析确定为属于链霉菌属(Streptomyces)一种.该菌具有内切β-1,4-葡聚糖酶活性但不具有糖苷酶活性.该菌所分泌的内切β-1,4-葡聚糖酶活性最大可达8.25 U/mg.菌株分泌酶活性的最适pH值为6～7,最适温度为60℃.从家白蚁中肠分离得到这一具内切葡聚糖酶活性的菌株表明,家白蚁中肠细菌可以通过分泌内切葡聚糖酶与白蚁内源性内切葡聚糖酶一道参与食物中纤维素的降解.     

噬菌蛭弧菌的分离及初步鉴定

采用双层平板法,以滤膜过滤的方法来收集噬菌蛭弧菌,以嗜水气单胞菌(Aeromonas hudrophila)、荧光假单胞菌(Pseudomonas fluorescent)和绿脓杆菌(Pseudomonas aeruginosa)为宿主菌,进行噬菌蛭弧菌的分离研究;并在此基础上,通过接触酶检测和寄生性确认对噬菌蛭弧菌(Bdellovibrio bacteriovorus)进行了初步的鉴定.结果表明未使用滤膜过滤,采用自来水琼脂双层平板法分离噬菌蛭弧菌的效果较好;并经过接触酶和寄生性检测初步鉴定此BD-SPOI菌株为噬菌蛭弧菌.     

Change in surface properties of Microthrix parvicella upon addition of polyaluminium chloride as characterized by atomic force microscopy

The filamentous bacterium Microthrix parvicella causes severe separation and foaming problems at wastewater treatment plants (WWTPs). An effective control of the bacterium in activated sludge WWTPs can be accomplished by dosage with polyaluminium chloride (PAX-14). The purpose of this study was to investigate whether addition of PAX-14 affects surface properties such as the hydrophobicity of the bacterium and to study the exopolymers of M. parvicella that host surface-associated enzymes. To this end, force measurements by atomic force microscopy were carried out to measure the interactions between hydrophilic and hydrophobized tips and the bacterium surface. Addition of PAX-14 caused no changes in the hydrophobicity of the bacterium surface but the data indicate that it collapsed the polymeric layer likely due to electrostatic screening. It is concluded that the collapse of the polymeric layer may affect the transport of substrates (eg free fatty acids) to the bacterium and hence the competitiveness of M. parvicella compared to the other bacteria present in activated sludge.     

Shotgun genome sequence of the large purple photosynthetic bacterium Rhodospirillum photometricum DSM122

Here, we present the shotgun genome sequence of the purple photosynthetic bacterium Rhodospirillum photometricum DSM122. The photosynthetic apparatus of this bacterium has been particularly well studied by microscopy. The knowledge of the genome of this oversize bacterium will allow us to compare it with the other purple bacterial organisms to follow the evolution of the photosynthetic apparatus.     

A Stochastic Analysis of a Brownian Ratchet Model for Actin-Based Motility

In recent single-particle tracking (SPT) measurements on Listeria monocytogenes motility in cells [Kuo and McGrath (2000)], the actin-based stochastic dynamics of the bacterium movement has been analyzed statistically in terms of the mean-square displacement (MSD) of the trajectory. We present a stochastic analysis of a simplified polymerization Brownian ratchet (BR) model in which motions are limited by the bacterium movement. Analytical results are obtained and statistical data analyses are investigated. It is shown that the MSD of the stochastic bacterium movement is a monotonic quadratic function while the MSD for detrended trajectories is linear. Both the short-time relaxation and the long-time kinetics in terms the mean velocity and effective diffusion constant of the propelled bacterium are obtained from the MSD analysis. The MSD of the gap between actin tip and the bacterium exhibits an oscillatory behavior when there is a large resistant force from the bacterium. For comparison, a continuous diffusion formalism of the BR model with great analytical simplicity is also studied.     

Effects of antibiotics on the early infection process of a macronuclear endosymbiotic bacterium Holospora obtusa of Paramecium caudatum

We examined the effects of antibiotics involved in bacterial DNA, RNA and protein synthesis and host protein synthesis on the early infection process of the bacterium Holospora obtusa, a macronucleus-specific symbiont of the ciliate Paramecium caudatum. Infection of the host macronucleus by the bacterium was not inhibited by mitomycin C, rifampicin and chloramphenicol. However, ingestion of the bacterium into the host digestive vacuoles and escape of the bacterium from the vacuoles to the host cytoplasm were significantly arrested with emetine. The results suggest that newly synthesized host proteins play an important role in the early infection process.     

The drug resistance of Hydrogenobacter thermophilus strain TK-6

Abstract Hydrogenobacter thermophilus is an extremely thermophilic and obligately autotrophic hydrogen-oxidising bacterium with various unusual properties and believed to occupy a unique taxonomic position. Inhibitory patterns of various antibiotics on the cell growth of H. thermophilus strain TK-6 clearly showed that the bacterium possessed prokaryote-type systems of DNA, RNA and protein syntheses. Effect of ionophore antibiotics supported that the bacterium was a Gram-negative bacterium, but high sensitivities against macrolide and some other antibiotics and insensitivity against polymyxin B were unusual as a Gram-negative eubacterium.
Growth inhibition by cell wall synthesis inhibitors revealed the existence of peptidoglycan on the surface of H. thermophilus , but ineffectiveness of cell wall lytic enzymes (lysozyme and lysostaphin) on intact cells and purified cell wall strongly suggested the uniqueness of the cell wall structure of the bacterium.     

Capsule-transmitted gut symbiotic bacterium of the Japanese common plataspid stinkbug, Megacopta punctatissima.

The Japanese common plataspid stinkbug, Megacopta punctatissima, deposits small brown particles, or symbiont capsules, on the underside of the egg mass for the purpose of transmission of symbiotic bacteria to the offspring. We investigated the microbiological aspects of the bacteria contained in the capsule, such as microbial diversity, phylogenetic placement, localization in vivo, and fitness effects on the host insect. Restriction fragment length polymorphism analysis of 16S ribosomal DNA clones revealed that a single bacterial species dominates the microbiota in the capsule. The bacterium was not detected in the eggs but in the capsules, which unequivocally demonstrated that the bacterium is transmitted to the offspring of the insect orally rather than transovarially, through probing of the capsule content. Molecular phylogenetic analysis showed that the bacterium belongs to the gamma-subdivision of the Proteobacteria. In adult insects the bacterium was localized in the posterior section of the midgut. Deprivation of the bacterium from the nymphs resulted in retarded development, arrested growth, abnormal body coloration, and other symptoms, suggesting that the bacterium is essential for normal development and growth of the host insect.     

The basis of the alkalophilic property of a species of bacillus.

An alkalophilic bacterium belonging to the genus Bacillus was isolated from an indigo ball. The bacterium exhibited a maximum growth rate at pH 10-0 TO 10-5. The incorporation of 14C-labelled amino acids or [14C]uracil, uptake of 14C-labelled alpha-amino isobutyric acid into the bacterium and oxygen consumption of the bacterium with amino acids as substrates were all maximum at pH 9-0 to 10-5. The uptake of [U-14C]glucose into the organism and oxygen consumption with carbohydrates, on the other hand, showed little variation of rate in the pH 8 to 10 region. The oxygen consumption of intact bacteria or protoplasts in culture medium was maximum at pH 10. The membrane of the bacterium oxidized NADH maximally at pH 7-5, and ATPase bound to the membrane exhibited maximum activity at pH 7.L-Lactate, L-alanine and malate dehydrogenases in the soluble fraction exhibited maximum activities at pH 7-4 to 8-4. The alkalophilic property of the bacterium may be due to the behaviour of the membrane towards charged substances admitted into the organisms.     

Effects of bacterial prey species and their concentration on growth of the amoebae Acanthamoeba castellanii and Hartmannella vermiformis

Two amoebae were presented with six bacterial prey at a range of concentrations, and the growth parameters of the amoebae were deduced. All but one bacterium (Synechococcus) resulted in a positive growth response, but the gram-positive bacterium Staphylococcus aureus proved to be difficult to digest and the heavily pigmented bacterium Klebsiella ozaenae induced unusual amoebic behavior prior to ingestion.     

Ultrastructural characterization of the prokaryotic symbiosis in "Chlorochromatium aggregatum"

The phototrophic consortium "Chlorochromatium aggregatum" currently represents the most highly developed interspecific association of bacteria and consists of green sulfur bacteria, so-called epibionts, surrounding a central, motile, chemotrophic bacterium. In order to identify subcellular structures characteristic of this symbiosis, consortia were studied by a combination of high-resolution analytical scanning electron microscopy, transmission electron microscopy, and three-dimensional reconstruction and image analyses. Epibionts are interconnected and to a lesser extent are also connected with the central bacterium, by electron-dense, hair-like filaments. In addition, numerous periplasmic tubules extend from the outer membrane of the central bacterium and are in direct contact with the outer membrane of the epibionts. In each epibiont cell, the attachment site to the central bacterium is characterized by the absence of chlorosomes and an additional 17-nm-thick layer (epibiont contact layer [ECL]) attached to the inner side of the cytoplasmic membrane. The ECL is only occasionally observed in pure cultures of the epibiont, where it occurs in about 10 to 20% of the free-living cells. A striking feature of the central bacterium is the presence of one or two hexagonally packed flat crystals (central bacterium crystal [CBC]) per cell. The CBC reaches 1 microm in length, is 35 nm thick, and consists of bilayers of subunits with a spacing of 9 nm. A detailed model for consortia is presented, summarizing our conclusions regarding (i) cohesion of the cells, (ii) common periplasmic space between the central bacterium and the epibiont, (iii) ECL as a symbiosis-specific structure, and (iv) formation of the interior paracrystalline structures, central bacterium membrane layer, and CBC.