V max per bacterium and turnover rate per bacterium for glucose mineralization in natural waters

Specific activity of aquatic bacteria, which indicates average heterotrophic activity per bacterial cell, was determined asV _max per bacterium and turnover rate per bacterium for glucose mineralization at different sites (river and estuary) in north Humberside, northeast England.V _max per bacterium ranged from 0.05×10⁻¹³ to 52.2×10⁻¹³ mg/h and turnover rate per bacterium from 0.05×10⁻⁸ to 88.3×10⁻⁸ ml/h. Highest mean values were found at river sites and the lowest at an outer estuary site, although there was considerable variation at each site and ranges from all sites overlapped. Also, ranges ofV _max per bacterium from Humberside sites in general overlapped published ranges for sites in other geographical areas.V _max per bacterium and turnover rate per bacterium were significantly correlated with some environmental variables, which suggests that they are of ecological significance.     

Infection of potato tubers with soft rot bacteria

Stolons attached to developing potato tubers were inoculated with the soft rot bacterium Erwinia carotovora var. atroseptica. Almost all the stolons rotted, but soft rots developed in less than 10% of new tubers; the bacterium was isolated later from these tubers. No rots developed in the other tubers but the bacterium was later isolated from about half of them. It could not be isolated from tubers attached to inoculated stolons where the rot on them did not extend to the tuber or from tubers attached to stolons that were not inoculated though many of these rotted. The bacterium was reisolated from almost all arrested lesions in tubers inoculated 8 month earlier with E. carotovora var. atroseptica. Blackleg did not develop from plants grown fom these tubers under various soil conditions. It did develop in a large proportion of plants from tubers inoculated shortly before planting and grown in cool, wet soil. Less than 1% blackleg developed in plants grown from tubers from plants with blackleg or from plants immediately adjacent. The presence of pectolytic bacteria and E. caratovora var. atroseptica in seed and new tubers was investigated during June, July and August. Although E. caratovora var. atroseptica was obtained from c. 40% tubers, only c. 0·3% of c. 8400 plants developed blackleg. The bacterium was isolated from only three of 160 new tubers sampled during the summer.     

Symbiotic relationship between <Emphasis Type="Italic">Microbacterium</Emphasis> sp. SK0812 and <Emphasis Type="Italic">Candida tropicalis</Emphasis> SK090404

A bacterium growing inside yeast cytoplasm was observed by light microscope without staining. The bacterium was separately stained from yeast cell by a fluorescent dye, 4′,6-diamidino-2-phenylindole (DAPI). The bacterium actively moved inside yeast cytoplasm and propagated in company with the yeast growth. The bacterium was separated from the yeast cytoplasm by selective disruption of yeast cells and the yeast without the intracellular bacterium (YWOB) was obtained by selective inactivation of bacterial cells. The yeast and the intracellular bacterium were identified as Candida tropicalis and Microbacterium sp., respectively. The length of Microbacterium sp. and C. tropicalis measured with SEM image was smaller than 0.5 μm and was larger than 5 μm, respectively. The yeast with the intracellular bacterium (YWIB) grew in a starch-based medium but the YWOB was not C. tropicalis has neither extracellular nor intracellular saccharification enzyme. Glucose was produced from starch by the extracellular crude enzyme (culture fluid) of Microbacterium sp. YWIB produced significantly more ethanol from glucose than YWOB but did not from starch. Conclusively, C. tropicalis is thought to catabolize starch dependent upon Microbacterium sp. growing in its cytoplasm and furnish stable habitat for the Microbacterium sp.     

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.     

Fractional Analyses of Soybean Sterols in Four Classes

A well growing methane oxidizing bacterium was isolated in pure culture from a natural source through studying production of single cell protein. This bacterium was identified as a new species Methylomonas flagellata. It was shown to be a gram-negative rod, 1.0 to 1.2 by 2.0 to 3.0 μ, and motile by means of polar flagella. Formation of a type of “immature cysts” was observed.

This bacterium showed relatively high growth rate of μ=0.17 hr^?1 for a pure methane oxidizing bacterium.     

Lysis of Aphanizomenon flos-aquae (Cyanobacterium) by a bacterium Bacillus cereus

A phytoplankton-lytic (PL) bacterium, Bacillus cereus, capable of lysing the bloom-forming cyanobacterium Aphanizomenon flos-aquae was isolated from Lake Dianchi of Yunnan province, China. This bacterium showed lytic activities against a wide range of cyanobacteria/algae, including A. flos-aquae, Microcystis viridis, Microcystis wesenbergi, Microcystis aeruginosa, Chlorella ellipsoidea, Oscillatoria tenuis, Nostoc punctiforme, Anabaena flos-aquae, Spirulina maxima, and Selenastrum capricornutum. Chlorophyll a contents, phycocyanin contents, and photosynthetic activities of the A. flos-aquae decreased evidently in an infected culture for a period. Bacterium B. cereus attacked rapidly A. flos-aquae cells by cell-to-cell contact mechanism. It was shown that the lysis of A. flos-aquae began with the breach of the cyanobacterial cell wall, and the cyanobacterial cell appeared abnormal in the presence of the PL bacterium. Moreover, transmission electron microscope examinations revealed that a close contact between the bacterium and the cyanobacterium was necessary for lysis. Some slime extrusions produced from B. cereus assisted the bacterial cells to be in close association with and lyse the cyanobacterial cells. These findings suggested that this bacterium could play an important role in controlling the Aphanizomenon blooms in freshwaters.     

“Candidatus Paraholospora nucleivisitans”, an intracellular bacterium in Paramecium sexaurelia shuttles between the cytoplasm and the nucleus of its host

An intracellular bacterium was discovered in two isolates of Paramecium sexaurelia from an aquarium with tropical fish in Münster (Germany) and from a pond in the Wilhelma zoological–botanical garden, Stuttgart (Germany). The bacteria were regularly observed in the cytoplasm of the host, but on some occasions they were found in the macronucleus of the host cell. In these cases, only a few, if any, bacteria were observed remaining in the cytoplasm. The bacterium was not infectious to P. sexaurelia or other species of Paramecium and appeared to be an obligate intracellular bacterium, while bacteria-free host cells were completely viable. The fluorescence in situ hybridisation (FISH) and comparative 16SrDNA sequence analyses showed that the bacterium belonged to a new genus, and was most closely, yet quite distantly, related to Holospora obtusa. In spite of this relationship, the new bacteria differed from Holospora by at least two biological features. Whereas all Holospora species reside exclusively in the nuclei of various species of Paramecium and show a life cycle with a morphologically distinct infectious form, for the new bacterium no infectious form and no life cycle have been observed. For the new bacterium, the name Candidatus Paraholospora nucleivisitans is suggested. The host P. sexaurelia is usually known from tropical and subtropical areas and is not a species typically found in Germany and central Europe. Possibly, it had been taken to Germany with fish or plants from tropical or subtropical waters. Candidatus Paraholospora nucleivisitans may therefore be regarded as an intracellular neobacterium for Germany.     

A conservative distribution of tridomain NDP-heptose synthetases in actinobacteria

Heptoses are important structural components of Gram-negative bacterium cell wall and participate in bacterial colonization, infection, and immune recognition. Current knowledge of NDP-heptose originating from d-sedoheptulose 7-phosphate in Grampositive bacterium remains limited. Here, in silico analysis suggested that the special tridomain NDP-heptose synthetases with isomerase, kinase, and nucleotidyltransferase activities are conservatively distributed in Actinobacteria class of Gram-positive bacterium. Enzymatical characterization of the tridomain proteins from different strains showed that they are involved in ADP-d-glycero-β-d-manno-heptose biosynthesis despite the unexpected discovery of kinase activities deficient in some proteins. The presence of three types of NDP-heptose synthetases in Gram-positive bacterium suggests that it is also a rich source of heptoses and the heptose moieties may play important roles in vivo. Our work updates the understanding of NDP-heptose biosynthesis in Gram-positive bacterium and lays a solid foundation for further physiological function explorations.

     

The Composition of Jerusalem Artichoke (Helianthus tuberosus L.) Spirits Obtained from Fermentation with Bacteria and Yeasts

The composition of spirits distilled from fermentation of Jerusalem artichoke (Helianthus tuberosus L.) tubers was compared by means of gas chromatography. The microorganisms used in the fermentation processes were the bacterium Zymomonas mobilis, strains 3881 and 3883, the distillery yeast Saccharomyces cerevisiae, strains Bc16a and D₂ and the Kluyveromyces fragilis yeast with an active inulinase. The fermentation of mashed tubers was conducted using a single culture of the distillery yeast Saccharomyces cerevisiae and the bacterium Zymomonas mobilis (after acid or enzymatic hydrolysis) as well as Kluyveromyces fragilis (sterilized mashed tubers). The tubers were simultaneously fermented by mixed cultures of the bacterium or the distillery yeast with K. fragilis. The highest ethanol yield was achieved when Z. mobilis 3881 with a yeast demonstrating inulinase activity was applied. The yield reached 94 % of the theoretical value. It was found that the distillates resulting from the fermentation of mixed cultures were characterized by a relatively lower amount of by‐products compared to the distillates resulting from the single species process. Ester production of 0.30–2.93 g/L, responsible for the aromatic quality of the spirits, was noticed when K. fragilis was applied for ethanol fermentation both in a single culture process and also in the mixed fermentation with the bacterium. Yeast applied in this study caused the formation of higher alcohols to concentrations of 7.04 g/L much greater than those obtained with the bacterium. The concentrations of compounds other than ethanol obtained from Jerusalem artichoke mashed tubers, which were fermented by Z. mobilis, were lower than those achieved for yeasts.     

The copper-resistant bacterium ACU isolated from the rhizosphere of Eichhornia crassipes (Mart.) increased the endurance of Potamogeton crispus L. to copper toxicity

Aims: This study aimed to develop endurance to copper stress in Potamogeton crispus L. by inoculation with the anti-copper strain ACU – a novel Enterobacteriaceae bacterium isolated from the rhizosphere of Eichhornia crassipes with high copper-removal ability. Methods and Results: A spherical copper-resistant bacterium, namely ACU, was isolated from the rhizosphere of E. crassipes. It was demonstrated to have substantial copper-removing capability, even at copper concentrations as high as 69 mg l⁻¹. The 16S rRNA gene sequence of ACU suggested it to be a novel Enterobacteriaceae bacterium most closely related to Providencia sp. With increasing copper concentrations, the growth rate of ACU gradually decreased with a delay in the logarithmic growth phase. ACU demonstrated high copper-removal ability at the lag phase when cultivated in media with high copper concentrations. A 48-kDa extracellular copper-binding protein was detected in ACU. When P. crispus was inoculated with ACU, the growth ability of P. crispus significantly improved at all the tested copper concentrations, and the lethal time for 10 mg l⁻¹ was delayed. Further study revealed that while ACU cells were rarely detected in the culture solution, they were associated with the surface of P. crispus. These findings indicated that ACU grew by anchoring itself on the surface of P. crispus and could increase the ability of P. crispus to resist copper toxicity. Conclusion: To the best of our knowledge, the Enterobacteriaceae bacterium ACU is a novel nonpathogenic bacterium with high copper-removing ability from water. Significance and Impact of the Study: This study demonstrated that the Enterobacteriaceae bacterium ACU has potential applicability for use in copper removal and in the protection of aquatic plants in copper-polluted water.     

Characterization of a bacterium isolated from amber

A bacterium has been isolated from Baltic amber, after it was soaked in ethanol and flamed. The bacterium was a Gram-positive aerobic spore-forming rod whose 16S rDNA sequence had a 99.6% homology to that of Bacillus subtilis. Accordingly, the bacterium was identified as a strain in the species Bacillus subtilis. Considering the isolation procedure that was employed, the isolate should not be a contaminant of the contemporary Bacillus population; however, it may not be considered as a bacterium trapped when the amber was formed. These results suggest that amber might contain bacteria that were derived from the environments in which the amber had been located.     

Hypersensitive response and acyl‐homoserine lactone production of the fire blight antagonists Erwinia tasmaniensis and Erwinia billingiae

Fire blight caused by the Gram‐negative bacterium Erwinia amylovora can be controlled by antagonistic microorganisms. We characterized epiphytic bacteria isolated from healthy apple and pear trees in Australia, named Erwinia tasmaniensis, and the epiphytic bacterium Erwinia billingiae from England for physiological properties, interaction with plants and interference with growth of E. amylovora. They reduced symptom formation by the fire blight pathogen on immature pears and the colonization of apple flowers. In contrast to E. billingiae, E. tasmaniensis strains induced a hypersensitive response in tobacco leaves and synthesized levan in the presence of sucrose. With consensus primers deduced from lsc as well as hrpL, hrcC and hrcR of the hrp region of E. amylovora and of related bacteria, these genes were successfully amplified from E. tasmaniensis DNA and alignment of the encoded proteins to other Erwinia species supported a role for environmental fitness of the epiphytic bacterium. Unlike E. tasmaniensis, the epiphytic bacterium E. billingiae produced an acyl‐homoserine lactone for bacterial cell‐to‐cell communication. Their competition with the growth of E. amylovora may be involved in controlling fire blight.     

Isolation of Highly Radioresistant Bacterium,Arthrobacter radiotolerans nov. sp.

A highly γ-ray resistant bacterium, which has not been described hitherto, has been isolated from water containing mud, fur and moss at a radioactive hot spring, Misasa, Tottori Prefecture, Japan, This bacterium was Gram-positive, non-sporulating, pink to red colored and pleomorphic rod at young stage and predominantly coccoid or small short rod at old. The radiosensitivity of this bacterium was lower than that of well-known bacterium Micrococcus radio- durans. When its exponentially growing cells were irradiated in buffer solution aerated sufficiently at room temperature, shoulder dose and D₀ were calculated to be 6 × 10⁵ and 1 × 10⁶ rads, respectively. The morphological, cultural and physiological characteristics of the bacterium have been studied. These attributes suggested that the organism was a new species, and the name Arthrobacter radiotolerans has been assigned with respect to its high radioresistance.     

Susceptibility of European catfish (Silurus gianis) to Edwardsiella ictaluri

European catfish (Silurus glanis) were tested for their susceptibility to the bacterium Edwardsiella ictaluri. The LD₅₀ of E. ictaluri when injected into European catfish was 5.4 × 10⁶ compared to 7.1 times; 10⁴ for channel catfish (Ictalurus punctatus). E. ictaluri was isolated from dead and moribund European catfish and the bacterium was also detected in kidney smears by an indirect fluorescent antibody (FA) technique. The bacterium was not isolated or detected by FA from surviving fish 15 days after injection. No clinical signs of E. ictaluri infection were noted in European catfish, but these were prevalent in the channel catfish. These experiments indicate that under experimental conditions European catfish are not as susceptible to E. ictaluri as channel catfish.     

A New Synthesis of (E,E)-8, 10-Dodecadien-1-ol,Sex Pheromone of Codling Moth

A methanol-utilizing bacterium, which produced red to pink pigments and assimilated methanol via icl^- serine pathway, was isolated from soil and tentatively designated as Pseudomonas MS 31. This bacterium produced L-serine when glycine was added to the growth medium at the late exponential phase of growth. The cells showed high L-serine degradation activity. Chelating agents and some metal ions, which inhibited L-serine degradation, stimulated the L-serine accumulation. In the presence of 0.1 ? 1 mM EDTA, o-phenanthroline, 8-hydroxyquinoline, α,α'-dipyridyl, cobalt sulfate or nickel sulfate, this bacterium produced 0.7?2.1mg L-serine from 4mg glycine per ml culture.     

Isolation of a gram-positive bacterium effective in suppression of brown blotch disease of cultivated mushrooms,Pleurotus ostreatus andAgaricus bisporus, caused byPseudomonas tolaasii

A Gram-positive bacterium was isolated from a rottingPleurotus ostreatus fruiting body that markedly reduced the level of extracellular toxins (i.e., tolaasins) produced byPseudomonas tolaasii, the most destructive pathogen of cultivated mushrooms. The isolated bacterium is saprophytic but not parasitic nor pathogenic toP. ostreatus. A low ratio, ca. 10⁻³ cells of the isolated bacterium for oneP. tolaasii cells, was sufficient for detoxification in vitro. Inoculation of the isolated bacterium prevents the development of bacterial disease inP. ostreatus andAgaricus bisporus. The suppression of the disease development, however requires the initial cell density equivalent to ca. 10⁻¹ cells of the isolated bacterium for one cells of the pathogen. The effects is ascribed to the inactivation of tolaasin by the live, suppressive bacterial cells, and not to metabolites secreted from the organism into culture media. Examination by conventional bacteriological tests and with testing kits, i.e., MicroStation^TMSystem Release 3.5 (Biolog Inc., Hayward, CA), ATB Expression (bioMerieux Inc. Japan) and VITEK (bioMerieux Inc. Japan), failed to assign the organism to any defined bacterial genus. The suppressive bacterium may be useful in future for the development of biocontrol system and/or the construction of genetically modified edible fungi resistant to the disease caused byP. tolaasii.     

A diazotrophic bacterial endophyte isolated from stems of Zea mays L. and Zea luxurians Iltis and Doebley

The apoplastic fluids of field-grown Zea mays and Zea luxurians plants were isolated from surface sterilized stem tissue by centrifugation and spread on agar plates containing a nitrogen-free, defined medium. The predominant bacterium isolated from these plates was characterized further. The ability of this bacterium to fix nitrogen was confirmed by its ability to grow on a semi-solid, nitrogen-free medium and reduce ¹⁵N₂ to ¹⁵NH₃ and acetylene to ethylene. Protions of the nifH and 16S rRNA genes from this organism were amplified by PCR and sequenced. The nifH gene, which codes for dinitrogenase reductase, from this organism is closely related to nifH from Klebsiella pneumoniae. Similarly, the 16S rRNA gene sequences and carbon utilization tests grouped it closely with K. pneumoniae. Based an these data, the isolates from Z. mays and Z. luxurians are tentatively classified as Klebsiella spp. (Zea). The ability of this bacterium to contribute to the nitrogen economy of the corn plant is unknown.     

Purification and physicochemical properties of malate dehydrogenase from bacteria of the genus Beggiatoa

Homogeneous malate dehydrogenase (MDH) with a specific activity of 20-24 units per mg protein was purified from the sulfur bacterium Beggiatoa leptomitiformis strain D-402 grown organotrophically and lithotrophically and from the organotrophic bacterium Beggiatoa alba. MDHs from the B. leptomitiformis strain D-402 grown under organotrophic conditions and from B. alba are homodimers with the subunit molecular weight of 40 kD. Tetrameric MDH is formed in B. leptomitiformis strain D-402 grown under lithotrophic conditions. The dimeric and tetrameric forms of MDH from B. leptomitiformis D-402 display some differences in kinetic properties.     

优异杂交水稻亲本灌浆期种子内生细菌多样性研究

通过传统微生物培养方法,对处于灌浆期的杂交水稻亲本"深08S"、"和620S"及"16A007"种子内生细菌群落结构多样性进行研究。实验表明,处于灌浆期的杂交水稻亲本种子仍然存在内生细菌群落结构的多样性。"深08S"种子内生细菌含6个OTU,第一优势菌属为Pantoea,丰度为52.04%,第二和第三优势菌属分别为Pseudomonas和Rhizobium;"和620S"种子内生细菌含10个OTU,第一优势菌属为Pantoea,丰度为69.02%,第二优势菌属为Pseudomonas,并列第三优势菌属为Rhizobium和Sphingomonas;"16A007"种子内生细菌含11个OTU,第一优势菌属为Pseudomonas,丰度为45.12%,第二优势菌属和第三优势菌属分别为Pantoea和Sphingomonas。由研究结果可见,具有遗传相关性的水稻种子"深08S"和"和620S"内生细菌的第一和第二优势菌属相同,同时,三种水稻亲本种子优势菌属都有Pantoea和Pseudomonas,表明水稻种子基因型对其内生细菌结构多样性具有一定的影响。     

Taxonomic Study of a Marine Bacterium Producing Guluronate Lyase

A marine bacterium that secretes a novel guluronate lyase that is heat- and denaturants-durable, has been isolated from the intestine contents of a red sea bream, Pagrus major. To characterize this marine bacterium, we attempted taxonomic study with respect to eleven characteristics used for the specification with an electron microscope photograph. The findings showed that the marine bacterium is a member of the genus Vibrio.