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.     

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.     

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.     

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.     

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。     

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.     

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.     

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.     

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.     

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.     

Determination of phenanthrene bioavailability by using a self-dying reporter bacterium: test with model solids and soil

The present study was conducted to investigate the performance and feasibility of a self-dying reporter bacterium to visualize and quantify phenanthrene bioavailability in soil. The self-dying reporter bacterium was designed to die on the initiation of phenanthrene biodegradation. The viability of the reporter bacterium was determined by a fluorescence live/dead cell staining method and visualized by confocal laser scanning microscopic observation. Phenanthrene was spiked into four types of model solids and a sandy loam. The bioavailability of phenanthrene to the reporter bacterium was remarkably declined with the hydrophobicity of the model solids: essentially no phenanthrene was biodegraded in the presence of 9-nm pores and about 35.8% of initial phenanthrene was biodegraded without pores. Decrease in bioavailability was not evident in the nonporous hydrophilic bead, but a small decrease was observed in the porous hydrophilic bead at 1000 mg/kg of phenanthrene. The fluorescence intensity was commensurate with the extent of phenanthrene biodegradation by the reporter bacterium at the concentration range from 50 to 500 mg/kg. Such a quantitative relationship was also confirmed with a sandy loam spiked up to 1000 mg/kg of phenanthrene. This reporter bacterium may be a useful means to determine phenanthrene bioavailability in soil.     

Alkanindiges hongkongensis sp. nov. A novel Alkanindiges species isolated from a patient with parotid abscess

A bacterium was isolated from the abscess pus of a 72-year-old patient with Warthin's tumor and parotid abscess. The cells were aerobic, non-motile, Gram-negative but difficult to be destained, non-sporulating, coccobacillus. The bacterium grew poorly on sheep blood agar and MacConkey agar as non-hemolytic colonies of 0.5 mm in diameter after 24h of incubation at 37 degrees C in ambient air. Growth was enhanced by Tween 80. It produces catalase but not cytochrome oxidase. Sequencing of the cloned 16S rRNA PCR products of the bacterium revealed three different 16S rRNA gene sequences, with 12 - 31 bp differences among them. Phylogenetic analysis showed that the bacterium is closely related to Alkanindiges illinoisensis, with 5.0 - 5.9% differences between the 16S rRNA gene sequence of the bacterium and that of A. illinoisensis. Tryptophan auxotrophic strain of Acinetobacter trpE27 transformed with DNA extracted from the bacterium was unable to grow on tryptophan deficient medium, indicating that the bacterium was not a strain of Acinetobacter. The G+C content of the bacterium (mean +/-SD) was 46.9+4.3%. A new species, Alkanindiges hongkongensis sp. nov., is proposed, for which HKU9T is the type strain. Isolates with "small colonies" that are apparently Acinetobacter-like species should be carefully identified. Growth enhancement with aliphatic hydrocarbons should be looked for and 16S rRNA gene sequencing performed in order to find more potential cases of Alkanindiges infections, as well as to define the epidemiology, clinical spectrum, and outcome of infections associated with this genus.     

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.     

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.     

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.     

Initial degradation of dimethylphthalate by esterases from Bacillus species

Dimethylphthalate (DMP), one of the phthalate esters, is used in the manufacture of plasticizers, insect repellents, and synthetic fibers, and contributes to environmental pollution. In the present study, we report a novel bacterium belonging to the Bacillus sp., which has the ability to utilize DMP as the sole source of carbon. The esterases from the cell-free extract of the Bacillus de-esterified DMP. Native polyacrylamide gel electrophoresis showed the presence of four isoesterases designated Et1--4. The isoesterases Et-4 and Et-1 showed a higher preference towards DMP hydrolysis as compared with Et-2 and 3. A megaplasmid of about 60 kb was detected in this bacterium. The ability of this bacterium to utilize DMP as the sole source of carbon was lost upon plasmid curing. The isoesterases Et-1--4 were absent in the cell-free extracts of the cured bacterium. The results from our studies clearly demonstrate that de-esterification is the initial step in the degradation of DMP and the genes for these esterases seem to be harbored on the plasmid in this bacterium.     

Isolation and partial characterization of bacteria in an anaerobic consortium that mineralizes 3-chlorobenzoic Acid

A methanogenic consortium able to use 3-chlorobenzoic acid as its sole energy and carbon source was enriched from anaerobic sewage sludge. Seven bacteria were isolated from the consortium in mono- or coculture. They included: one dechlorinating bacterium (strain DCB-1), one benzoate-oxidizing bacterium (strain BZ-2), two butyrate-oxidizing bacteria (strains SF-1 and NSF-2), two H(2)-consuming methanogens (Methanospirillum hungatei PM-1 and Methanobacterium sp. strain PM-2), and a sulfate-reducing bacterium (Desulfovibrio sp. strain PS-1). The dechlorinating bacterium (DCB-1) was a gram-negative, obligate anaerobe with a unique "collar" surrounding the cell. A medium containing rumen fluid supported minimal growth; pyruvate was the only substrate found to increase growth. The bacterium had a generation time of 4 to 5 days. 3-Chlorobenzoate was dechlorinated stoichiometrically to benzoate, which accumulated in the medium; the rate of dechlorination was ca. 0.1 pmol bacterium day. The benzoate-oxidizing bacterium (BZ-2) was a gram-negative, obligate anaerobe and could only be grown as a syntroph. Benzoate was the only substrate observed to support growth, and, when grown in coculture with M. hungatei, it was fermented to acetate and CH(4). One butyrate-oxidizing bacterium (NSF-2) was a gram-negative, non-sporeforming, obligate anaerobe; the other (SF-1) was a gram-positive, sporeforming, obligate anaerobe. Both could only be grown as syntrophs. The substrates observed to support growth of both bacteria were butyrate, 2-dl-methylbutyrate, valerate, and caproate; isobutyrate supported growth of only the sporeforming bacterium (SF-1). Fermentation products were acetate and CH(4) (from butyrate, isobutyrate, or caproate) or acetate, propionate, and CH(4) (from 2-dl-methylbutyrate or valerate) when grown in coculture with M. hungatei. A mutualism among at least the dechlorinating, benzoate-oxidizing, and methane-forming members was apparently required for utilization of the 3-chlorobenzoate substrate.     

巴马小型猪大肠埃希菌的分离鉴定及耐药性试验

目的分离鉴定引起巴马小型猪腹泻的细菌并筛选出对其敏感的特效药物。方法通过常规细菌学检测、分子生物学鉴定、生化试验等方法对疑似细菌感染的巴马小型猪进行分析,同时选用呋喃妥因、美满霉素、庆大霉素等25种药物对分离的细菌进行药敏实验。结果通过以上实验判定巴马小型猪为大肠埃希菌感染引起的腹泻,血清型为O138;药敏试验分析结果表明,该菌株仅对青霉素、链霉素、头孢曲松和呋喃妥因4种药物敏感,对磷霉素、磺胺脒、左氟沙星等高度耐药。结论大肠埃希菌广泛存在耐药性,该研究结果为防治相关实验动物大肠埃希菌感染提供理论依据。