Effects of hydrostatic pressure, agitation and CO2 stress on Phytophthora nicotianae zoospore survival.

BACKGROUND: Phytophthora nicotianae Breda de Haan is a common pathogen of ornamental plants in recycled irrigation systems. In a previous study, annual vinca (Catharanthus roseus Don) inoculated with zoospore suspensions using a CO(2)-pressurized sprayer had less foliage blight than plants inoculated using a hand sprayer. Here, the impact of hydrostatic pressure, agitation and aeration with CO(2) on the survival of P. nicotianae zoospores was examined. RESULTS: Exposure of zoospores to 840 kPa hydrostatic pressure for 8 min or agitation at a mixing intensity (G) of 6483 s(-1) for 4 min at 22-23 degrees C did not kill zoospores, but resulted in viable cysts. Motile and forcefully encysted zoospores of P. nicotianae were equally infectious on vinca or lupine (Lupinus polyphylus Lindl.). Bubbling CO(2) into zoospore-infested water at 110.4 mL (0.2 g) min(-1) for 5 min caused 81% reduction in the number of germinated zoospores. Pressure at 630 kPa (16.3 g CO(2)) or 70 kPa (3.85 g CO(2)) facilitated CO(2) injection and shortened the zoospore inactivation time to 30 s. When air was bubbled through the suspension, germination was similar to the control. CONCLUSIONS: Exposure to CO(2) killed P. nicotianae zoospores in water. Neither pressure nor agitation had an effect on zoospore viability or infectivity. Based on results of this study, the authors designed a recycling CO(2) water treatment system that is currently under evaluation.

A Phytophthora sojae G-protein alpha subunit is involved in chemotaxis to soybean isoflavones.

For the soybean pathogen Phytophthora sojae, chemotaxis of zoospores to isoflavones is believed to be critical for recognition of the host and for initiating infection. However, the molecular mechanisms underlying this chemotaxis are largely unknown. To investigate the role of G-protein and calcium signaling in chemotaxis, we analyzed the expression of several genes known to be involved in these pathways and selected one that was specifically expressed in sporangia and zoospores but not in mycelium. This gene, named PsGPA1, is a single-copy gene in P. sojae and encodes a G-protein alpha subunit that shares 96% identity in amino acid sequence with that of Phytophthora infestans. To elucidate the function, expression of PsGPA1 was silenced by introducing antisense constructs into P. sojae. PsGPA1 silencing did not disturb hyphal growth or sporulation but severely affected zoospore behavior, including chemotaxis to the soybean isoflavone daidzein. Zoospore encystment and cyst germination were also altered, resulting in the inability of the PsGPA1-silenced mutants to infect soybean. In addition, the expressions of a calmodulin gene, PsCAM1, and two calcium- and calmodulin-dependent protein kinase genes, PsCMK3 and PsCMK4, were increased in the mutant zoospores, suggesting that PsGPA1 negatively regulates the calcium signaling pathways that are likely involved in zoospore chemotaxis.

The proportions of Streptomyces californicus and Stachybotrys chartarum in simultaneous exposure affect inflammatory responses in mouse RAW264.7 macrophages.

Adverse health outcomes associated with moisture-damaged buildings originate from an exposure consisting of complex interactions between various microbial species and other indoor pollutants. The concentrations and proportions of microbial components in such environments can vary greatly with the growth conditions. In this study, we aimed to evaluate the effects of simultaneous exposure with modified proportions of actinobacteria Streptomyces californicus and fungi Stachybotrys chartarum on inflammatory responses (cytokines macrophage inflammatory protein 2 [MIP2], interleukin 6 [IL-6] and tumor necrosis factor a [TNFa]; nitric oxide) and cytotoxicity (MTT-test and DNA content analysis) in mouse RAW264.7 macrophage cell line. Five different proportions of microbial spores were studied (Str. californicus: S. chartarum 10:1; 5:1; 1:1; 1:5; 1:10). RAW264.7 cells were coexposed to the total dose of 3x10(5) spores/ml for 24 h and also both of these microbial spores on their own at the respective doses. At least the 1.5-fold synergistic increase in cytokine production of RAW264.7 macrophages was detected when coexposure contained an equal amount or more fungal spores (S. chartarum) than bacterial spores (Str. californicus) compared to the sum response caused by these microbial spores separately. On the contrary, NO production after coexposure was nearly 40% less than the sum response induced by the microbial spores separately, when coexposure contains 5 times more bacterial than fungal spores. In addition, coexposure slightly changed the cytotoxic potency of the spores. The present results revealed that mutual proportions of fungal and bacterial spores in simultaneous exposure affect the nature of their interactions leading to increased or suppressed production of inflammatory mediators in RAW264.7 macrophages.

Comparison of the toxicity of reference mycotoxins and spore extracts of common indoor moulds.

There is an unclear endangering potential by toxic influences of inhaled conidiospores and therefore the conidia of indoor mould species were cultured and toxicologically examined after their mechanical disintegration. For this purpose high-performance liquid chromatography (HPLC) and three colorimetric bioassays, the PTGT (pollen tube growth test), the MB (methylene blue) and the MTT (methylthiazoltetrazolium) assay were applied. The sensitivity of the biological methods was evaluated by using 12 reference mycotoxins and 3 structural cell wall components. Only in one extract of disintegrated spores (Aspergillus fumigatus) a mycotoxin (0.22 microg gliotoxin/6.2 x 10(8) spores) was determined. All nine spore extracts, however, turned out to be cytotoxic and in this case the MTT assay was remarkably more sensitive than the two other test methods. The IC50 values of six different spore extracts determined by the MTT assay were lower than 10(6) spores/well (well = 0.2 ml) whereas the IC50 values determined by the MB assay and PTGT were higher than 10(6) spores per 0.2 ml for each spore extract. An examination of four spore extracts, which were fractionated depending on their polarity by HPLC, showed that single substances as well as synergistic effects contribute to the toxic properties of the spores. The results of this work indicate a health hazard due to toxic effects after the inhalation of extremely high spore concentrations of indoor moulds. This risk will also exist if the spores do not contain any mycotoxins.

What can spores do for us?

Many organisms have the ability to form spores, a remarkable phase in their life cycles. Compared with vegetative cells, spores have several advantages (e.g. resistance to toxic compounds, temperature, desiccation and radiation) making them well suited to various applications. The applications of spores that first spring to mind are bio-warfare and the related, but more positive, field of biological control. Although they are often considered metabolically inert, spores can also be used as biocatalysts. Other uses for spores are found in the fields of probiotics, tumour detection and treatment, biosensing and in the "war against drugs".

Gill infection of Leporinus macrocephalus Garavello & Britski, 1988 (Osteichthyes: Anostomidae) by Henneguya leporinicola n. sp. (Myxozoa: Myxobolidae). Description, histopathology and treatment.

Piauçus (Leporinus macrocephalus), were raised in 300 m2 ponds (density of 10 fish/m2) presenting asphyxia signals and daily mortality of 27 fishes. Specimens with 8-cm total body length, were collected for necropsy. Mucus of body surface and pieces of organs were collected and examined microscopically, in wet mounts, stained or in histological sections. The smears examination showed the presence of several spores in the secondary lamellae of the gill filaments, identified as Henneguya leporinicola n.sp (Myxozoa: Myxobolidae). Histopathological study showed epithelial hyperplasia and fulfilling of the spaces between the secondary lamellae, congestion and telangiectasia sinusoidal. It was also observed hyperplasia of the goblet cells and several cysts of parasite with 70.3 microns diameter. Such cysts were situated among the secondary lamellae, covered or not by the hyperplasic epithelium. With this diagnostic, three applications of formalin solution 10 ml/m3 were carried out. Fifteen days after that, fish were examined again to ascertain whether the treatment was efficient on disease caused by the protozoa. The tissue alterations present in the gills after the treatment were just a moderate sinusoidal congestion and a slight epithelial hyperplasia on the base of the secondary lamellae.

Phalacrocorax olivaceus un huevo vector mecánico de henneguya sp en ecosistemas acuáticos del sur de Chile / Phalacrocorax olivaceus a new mechanical vector of henneguya sp in aquatic echosystems from the south of Chile

This is the first report of henneguya sp, a myxozoan parasite of fishes, in faeces of phalacrocorax olivaceus, a piscivorous bird, from Valdivia river, Chile. Phalacrocorax olivaceus would be a mechanical vector of henneguya sp an contributes to diseminate the infection in fishes

Lycopodium granuloma.

The spores of Lycopodium (L) clavatum were used as a component of a dusting powder in many hospitals during the 1920's and 1930's. When L spores enter surgical wounds a lesion clinically resembling tuberculosis or neoplasia may develop months or even years later. We recently encountered a case of L granuloma occurring in a patient 50 years after an appendectomy. Three additional cases found in the files of the AFIP are also reported.

Experimental study of the pathogenicity of aspergilli for mice.

The relative virulence was determined for 14 species of aspergilli, by inoculating normal mice intravenously with graded doses of spores. Eleven were found to possess some degree of virulence, whereas three others were avirulent. Members of the Aspergillus flavus group were the only species that consistently killed mice with doses as low as 10(4) viable spores. When the in vivo fate of spores was compared for a virulent and an avirulent strain of Aspergillus, spores of the latter were cleared rapidly from the liver and spleen but grew in the kidneys and brain, producing progressive disease. Mice which inhaled spores did not succumb, but macrophages washed from their lungs contained spores. A relationship of virulence to spore characteristics such as germination time, size, shape, and external markings could not be established. Virulence could not be related to aflatoxin production inasmuch as at least one virulent strain did not produce aflatoxin in vitro.