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121.
Background
The widely expressed Dps proteins, so named after the DNA-binding properties of the first characterized member of the family in Escherichia coli, are considered major players in the bacterial response to stress.Scope of review
The review describes the distinctive features of the “ferritin-like” ferroxidation reaction, which uses hydrogen peroxide as physiological iron oxidant and therefore permits the concomitant removal of the two reactants that give rise to hydroxyl radicals via Fenton chemistry. It also illustrates the structural elements identified to date that render the interaction of some Dps proteins with DNA possible and outlines briefly the significance of Dps–DNA complex formation and of the Dps interaction with other DNA-binding proteins in relation to the organization of the nucleoid and microbial survival.General significance
Understanding in molecular terms the distinctive role of Dps proteins in bacterial resistance to general and specific stress conditions.Major conclusions
The state of the art is that the response to oxidative and peroxide-mediated stress is mediated directly by Dps proteins via their ferritin-like activity. In contrast, the response to other stress conditions derives from the concerted interplay of diverse interactions that Dps proteins may establish with DNA and with other DNA-binding proteins. 相似文献122.
Kevin K. Schrader Anna Andolfi Charles L. Cantrell Alessio Cimmino Stephen O. Duke Weste Osbrink David E. Wedge Antonio Evidente 《化学与生物多样性》2010,7(9):2261-2280
Phytotoxic microbial metabolites produced by certain phytopathogenic fungi and bacteria, and a group of phytotoxic plant metabolites including Amaryllidacea alkaloids and some derivatives of these compounds were evaluated for algicide, bactericide, insecticide, fungicide, and herbicide activities in order to discover natural compounds for potential use in the management and control of several important agricultural and household structural pests. Among the various compounds evaluated: i) ophiobolin A was found to be the most promising for potential use as a selective algicide; ii) ungeremine was discovered to be bactericidal against certain species of fish pathogenic bacteria; iii) cycasin caused significant mortality in termites; iv) cavoxin, ophiobolin A, and sphaeropsidin A were most active towards species of plant pathogenic fungi; and v) lycorine and some of its analogues (1‐O‐acetyllycorine and lycorine chlorohydrate) were highly phytotoxic in the herbicide bioassay. Our results further demonstrated that plants and microbes can provide a diverse and natural source of compounds with potential use as pesticides. 相似文献
123.
Emilie Lefèvre Marlène Jobard Alexandre Bec Christian Amblard 《Journal of microbiological methods》2010,81(1):69-76
Recently, molecular environmental surveys of the eukaryotic microbial community in lakes have revealed a high diversity of sequences belonging to uncultured zoosporic fungi. Although they are known as saprobes and algal parasites in freshwater systems, zoosporic fungi have been neglected in microbial food web studies. Recently, it has been suggested that zoosporic fungi, via the consumption of their zoospores by zooplankters, could transfer energy from large inedible algae and particulate organic material to higher trophic levels. However, because of their small size and their lack of distinctive morphological features, traditional microscopy does not allow the detection of fungal zoospores in the field. Hence, quantitative data on fungal zoospores in natural environments is missing. We have developed a quantitative PCR (qPCR) assay for the quantification of fungal zoospores in lakes. Specific primers were designed and qPCR conditions were optimized using a range of target and non-target plasmids obtained from previous freshwater environmental 18S rDNA surveys. When optimal DNA extraction protocol and qPCR conditions were applied, the qPCR assay developed in this study demonstrated high specificity and sensitivity, with as low as 100 18S rDNA copies per reaction detected. Although the present work focuses on the design and optimization of a new qPCR assay, its application to natural samples indicated that qPCR offers a promising tool for quantitative assessment of fungal zoospores in natural environments. We conclude that this will contribute to a better understanding of the ecological significance of zoosporic fungi in microbial food webs of pelagic ecosystems. 相似文献
124.
Norbert Stoppacher Susanne Zeilinger Rainer Schuhmacher 《Journal of microbiological methods》2010,81(2):187-2038
In the present study we describe a method, which is based on solid phase microextraction (SPME) coupled to gas chromatography-mass spectrometry (GC-MS) and which can be used for the profiling of microbial volatile organic compounds (MVOCs) in the headspace (HS) of cultures of filamentous fungi. The method comprises the following successive steps: 1. growth of the fungus on a solid culture medium directly in headspace vials, 2. measurement of volatiles by HS-SPME-GC-MS, 3. deconvolution of mass spectra, 4. identification of volatiles by comparison of measured, deconvoluted mass spectra and linear temperature programmed retention indices (LTPRI) on two stationary GC phases with database entries and LTPRI published in the literature, and 5. profiling of the identified MVOCs.The developed method was successfully applied to cultures of the biocontrol fungus Trichoderma atroviride. An in-house library consisting of mass spectra and LTPRI values of fungal VOCs was established and used to study the profiles of MVOCs of this fungus. In total, 25 different MVOCs were identified by applying strict criteria (spectral match factor at least 90% and a maximum relative deviation of LTPRI of ± 2% from literature values). The MVOCs were assigned to the compound classes of alcohols, ketones, alkanes, furanes, pyrones (mainly the bioactive 6-pentyl-alpha-pyrone), mono- and sesquiterpenes, 13 of which have never been reported to be produced by Trichoderma spp. before. Eleven of these volatiles have been additionally confirmed using authentic standards. Finally, time course experiments and cultivation of T. atroviride in the presence of the mycotoxin fusaric acid demonstrated the potential of the method to study the dynamics of MVOC profiles as well as the effect of different environmental/biological conditions on the expression of MVOCs of filamentous fungi. 相似文献
125.
Sixteen new and one known metabolites 4-20 were obtained by incubation of tibolone (1) and hydroxytibolones (2 and 3) with various fungi. Their structures were elucidated by means of a homo and heteronuclear 2D NMR and by HREI-MS techniques. The relative stereochemistry was deduced by 2D NOESY experiment. Metabolites of tibolone (1) exhibited significant inhibitory activities against α-glucosidase and tyrosinase enzymes. Hydroxylations at C-6, C-10, C-11, C-15 positions and α,β-unsaturation at C-1/C-2, C-4/C-5 showed potent inhibitory activities against these enzymes. 相似文献
126.
Abstract Isolates of Aureobasidium pullulans which produce antibacterial metabolites were compared with non-antibiotic-producing isolates of Tremella foliacea and Trichosporon beigelii for their ability to inhibit growth of Pseudomonas syringae pv phaseolicola . The bacteria and fungi were co-inoculated on an artificial leaf surface under conditions of low and high water availability. Under conditions of excess moisture, antibiotic production gave no advantage to the Aureobasidium isolates, and all the yeasts were equally antagonistic. Under drier conditions the Aureobasidium isolates reduced the population of P. syringae by 96–99%, a result which was significantly different from that which occurred when the bacteria were co-inoculated with the other yeasts under these conditions. An antibacterial compound, similar to that produced in liquid culture by Aureobasidium , was detected in washings from the artificial leaf surface following growth of this species. 相似文献
127.
128.
Sponges (Porifera) are filter feeders that take up microorganisms from seawater and digest them by phagocytosis. At the same
time, many sponges are known to harbor massive consortia of symbiotic microorganisms, which are phylogenetically distinct
from those in seawater, within the mesohyl matrix. In the present study, feeding experiments were performed to investigate
whether phylogenetically different bacterial isolates, hereafter termed “food bacteria,” microbial seawater consortia, and
sponge symbiont consortia are taken up and processed differently by the host sponge. Aplysina aerophoba retained high numbers of bacterial isolates and microbial seawater consortia with rates of up to 2.76 × 106 bacteria (g sponge wet weight)–1 h–1, whereas the retention of sponge symbionts was lower by nearly two orders of magnitude [5.37 × 104 bacteria (g sponge wet weight)−1 h–1]. In order to visualize the processing of a food bacterium within sponge tissues, the green fluorescent protein-labeled Vibrio strain MMW1, which had originally been isolated from A. aerophoba, was constructed. Incubation of this strain with A. aerophoba and subsequent visualization in tissue cryosections showed its presence in the choanocytes and/or endopinacocytes lining
the canals but, unlike latex beads, not in deeper regions of the mesohyl, which suggests digestion of the bacteria upon contact
with the host. Denaturing gradient gel electrophoresis (DGGE) was performed on the incubation seawater to monitor the changes
in phylogenetic composition after incubation of the sponge with either seawater or sponge symbiont consortia. However, the
DGGE experiment provided no evidence for selective processing of individual lineages by the host sponge. In conclusion, this
study extends early studies by Wilkinson et al. (Proc R Soc London B 220:519–528, 1984) that sponges, here A. aerophoba, are able to differentiate between food bacteria and their own bacterial symbionts. 相似文献
129.
Akello J Dubois T Gold CS Coyne D Nakavuma J Paparu P 《Journal of invertebrate pathology》2007,96(1):34-42
Beauveria bassiana is considered a virulent pathogen against the banana weevil Cosmopolites sordidus. However, current field application techniques for effective control against this pest remain a limitation and an alternative method for effective field application needs to be investigated. Three screenhouse experiments were conducted to determine the ability of B. bassiana to form an endophytic relationship with tissue culture banana (Musa spp.) plants and to evaluate the plants for possible harmful effects resulting from this relationship. Three Ugandan strains of B. bassiana (G41, S204 and WA) were applied by dipping the roots and rhizome in a conidial suspension, by injecting a conidial suspension into the plant rhizome and by growing the plants in sterile soil mixed with B. bassiana-colonized rice substrate. Four weeks after inoculation, plant growth parameters were determined and plant tissue colonization assessed through re-isolation of B. bassiana. All B. bassiana strains were able to colonize banana plant roots, rhizomes and pseudostem bases. Dipping plants in a conidial suspension achieved the highest colonization with no negative effect on plant growth or survival. Beauveria bassiana strain G41 was the best colonizer (up to 68%, 79% and 41% in roots, rhizome and pseudostem base, respectively) when plants were dipped. This study demonstrated that, depending on strain and inoculation method, B. bassiana can form an endophytic relationship with tissue culture banana plants, causing no harmful effects and might provide an alternative method for biological control of C. sordidus. 相似文献
130.
Luis A. Materon Martha Martinez-Garcia Veronica McDonald 《World journal of microbiology & biotechnology》2007,23(9):1281-1287
Foodborne illness outbreaks involving cantaloupes have increased dramatically in the past 15 years in the United States and
other countries. The need for the identification of the microbial sources that contaminate cantaloupe rinds has been raised
by various investigators. This study was undertaken to identify the agricultural, industrial and human sources of microbial
contamination from the pre- to post-harvest operations of cantaloupes grown at ten different farms in southern Texas. Results
indicate that irrigation water contained a wide range of microorganisms that could cause human illness and were able to survive
on the rind of cantaloupes before, at, and after harvesting. Fungi, total aerobic bacteria and total coliform bacteria were
not completely eliminated by chlorinated water in the disinfection tanks of the six packinghouses under investigation. There
were significant (P < 0.05) reductions on rind populations of fungi and total aerobic bacteria as well as drastic reductions in total coliform
bacteria on the rinds after the disinfection and rinsing steps in all packing facilities. There was no evidence of the presence
of Escherichia coli O157:H7 on packed cantaloupes across packinghouses. Less than a geometric mean of 1 c.f.u. cm−2 of salmonellae were detected on the surface of packed cantaloupes in two of the packinghouses, and approximately ten times
more salmonellae were found on the packed fruit processed in the remaining packinghouses. A similar trend was observed with
listeriae. Results suggested that microbial loads originating from river water may survive on the rind or may re-infest cantaloupes
after the disinfection and rinsing process at the packinghouses. Disinfection techniques and aseptic handling of cantaloupes
at the packing facilities need a closer evaluation to ensure a safe product. 相似文献