ASEXUAL REPRODUCTION AND BEHAVIOR OF ZOOSPORES OF PHYTOPHTHORA MEGASPERMA VAR. SOJAE

1967 ◽  
Vol 45 (11) ◽  
pp. 1963-1981 ◽  
Author(s):  
H. H. Ho ◽  
C. J. Hickman
Keyword(s):  
Germ Tube ◽  
Solid Surfaces ◽  
Extreme Temperatures ◽  
Phytophthora Megasperma ◽  
Frequent Contact ◽  
Ph Values ◽  
Pure Cultures ◽  
And Behavior ◽  
Germ Tubes ◽  
Cyst Germination

A method was devised to produce abundant zoospores in distilled water suspension from pure cultures of Phytophthora megasperma var. sojae. Sporangia were predominantly non-papillate, but occasionally inconspicuously or conspicuously papillate, germinating with the formation of a delicate, evanescent vesicle. Proliferation of sporangia was observed.Flagella action of freely swimming zoospores was investigated photographically. Both flagella were proved to undulate. Zoospores remained motile longest at 15 °C. Motility was markedly reduced at extreme temperatures (5 and 36 °C), at extreme pH values (below 5.2 or above 9.25), or by mechanical disturbance, dilution, and frequent contact with solid surfaces. The fate of flagella during encystment was followed. Encysted zoospores germinated by germ tubes, or by secondary zoospores, or in rare cases, the germ tube was terminated by a miniature sporangium. Repeated emergence of zoospores was favored at 15 °C whereas total cyst germination and germ tube production was best at 25 °C and in the presence of nutrients.

FACTORS GOVERNING ZOOSPORE RESPONSES OF PHYTOPHTHORA MEGASPERMA VAR. SOJAE TO PLANT ROOTS

1967 ◽  
Vol 45 (11) ◽  
pp. 1983-1994 ◽  
Author(s):  
H. H. Ho ◽  
C. J. Hickman
Keyword(s):  
Root Exudate ◽  
Chemical Nature ◽  
Root Surface ◽  
Plant Roots ◽  
Root Tip ◽  
Phytophthora Megasperma ◽  
Negative Pole ◽  
New Feature ◽  
Germ Tubes ◽  
Cyst Germination

In the presence of plant roots, zoospores of Phytophthora megasperma var. sojae reacted in general as do other fungal zoospores: they were attracted to, and trapped in the immediate vicinity of the root surface, on which they encysted rapidly. Encysted zoospores formed a continuous sheath around the root, thickest just behind the root tip. Cyst germination was stimulated. Germ tubes were always initiated from the side of cysts closest to the root and grew towards it. In addition, a new feature was observed, suppression of repeated emergence of zoospores. Zoospore accumulation was nonspecific with respect to host and non-host, resistance, and susceptibility.Tests with exudates and extracts from roots of resistant and susceptible soybean varieties and a non-host, pea, confirmed the chemical nature of the stimulus inducing these responses. Zoospores observed in an electric field were not attracted towards either pole, but they were trapped and encysted rapidly around the negative pole. Cyst germination was not stimulated. Nevertheless, since encystment was more pronounced on root exudate agar mounted on the negative pole, electric charges on roots may also contribute to inducing early encystment of zoospores there.In an investigation of ions on zoospore responses, with ionic resins, all phases of zoospore response to roots, with the exception of attraction, occurred in the presence of hydrogen resin particles.

The requirements for bicarbonate and metabolism of the inducer during germ tube formation by Candida albicans

1988 ◽  
Vol 34 (11) ◽  
pp. 1183-1188 ◽  
Author(s):  
Jordan H. Pollack ◽  
Tadayo Hashimoto
Keyword(s):  
Candida Albicans ◽  
Germ Tube ◽  
Tube Formation ◽  
Factors Affecting ◽  
Ph Values ◽  
Germ Tubes

Factors affecting germ tube formation in Candida albicans at suboptimal temperatures were investigated. Candida albicans formed germ tubes between 22 and 30 °C in solution when incubated without shaking, in the presence of bicarbonate (2 mg mL−1). Other conditions depended on the inducer used. Proline could induce germ tube formation optimally only when its concentration was between 200 and 400 mM. A concentration of 0.05 mM N-acetylglucosamine was sufficient to induce germ tube formation. N-Acetylglucosamine could induce germ tube formation at 30 but not at 25 °C. N-Acetylglucosamine induced germ tube formation was most reproducible when the cells were first starved by incubation in water for 16–24 h at 20 °C. Germ tubes induced by proline could be formed at pH values between 3.8 and 9.0 at 30 °C, but only between 7.0 and 7.5 at 25 °C. The addition of 0.05 to 5 mM glucose to a 5 mM proline induction solution allowed germ tube formation at 30 but not at 25 °C. Glucose (400 mM) did not suppress germ tube formation at 30 °C but only 5 mM was sufficient to cause a 65% suppression at 25 °C. The results show the importance of CO2 and (or) bicarbonate to the induction of germ tube formation and are consistent with the metabolism of the inducer.

Incidence, Radioresistance, and Behavior of Psychrobacter spp. in Rabbit Meat

2005 ◽  
Vol 68 (3) ◽  
pp. 538-543 ◽  
Author(s):  
JOSÉ M. RODRÍGUEZ-CALLEJA ◽  
MARGARET F. PATTERSON ◽  
ISABEL GARCÍA-LÓPEZ ◽  
JESÚS A. SANTOS ◽  
ANDRÉS OTERO ◽  
...  
Keyword(s):  
Similar Increase ◽  
Chilled Storage ◽  
Relative Incidence ◽  
Spoilage Bacteria ◽  
Brochothrix Thermosphacta ◽  
Pure Cultures ◽  
Maximum Cell ◽  
Rabbit Meat ◽  
Cell Densities ◽  
And Behavior

The relative incidence of Psychrobacter spp. in rabbit meat, the radioresistance of these bacteria, and the growth of nonirradiated and irradiated psychrobacter isolates, alone and in coculture, during chilled storage of inoculated sterile rabbit meat was investigated. Psychrobacter spp. accounted for 4.2% of the storage psychrotrophic flora of 30 rabbit carcasses. The radiation D10-values of 10 Psychrobacter isolates, irradiated at 4°C in minced rabbit meat, ranged from 0.8 to 2.0 kGy, with significant (P < 0.05) differences among strains. Over 12 days of storage at 4°C, pure cultures of two nonirradiated psychrobacter strains (D10 = 2 kGy) were capable of substantial increases (up to 3 log CFU/g) in sterile rabbit meat, but when the fastest growing strain was cocultured with Pseudomonas fluorescens and Brochothrix thermosphacta isolates, maximum cell densities and growth rates were significantly (P < 0.01) lower. After irradiation (2.5 kGy) of pure cultures in sterile rabbit meat, surviving cells of both Psychrobacter strains decreased for a period of 5 to 7 days and then resumed multiplication that, at day 12, resulted in a similar increase (1.6 to 1.7 log CFU/g) over initial survivor numbers. When irradiated in combination with the spoilage bacteria, one of the strains required 12 days to reach initial numbers. In conclusion, Psychrobacter spp. are radioresistant nonsporeforming bacteria with a low relative incidence among the storage flora of rabbit meat, unable to compete with food spoilage bacteria in this ecosystem and apparently not a major contributor to the spoilage of rabbit meat after irradiation.

scholarly journals Screening of a Soil Bacteria Collection for the Production of Alkali Thermostable Xylanases

2018 ◽  
Vol 10 (8) ◽  
pp. 232
Author(s):  
C. R. Sampaio ◽  
C. G. S. Silva ◽  
É. C. T. Anjos ◽  
R. P. M. Fernandes ◽  
M. F. Fernandes
Keyword(s):  
Selection Criteria ◽  
Soil Bacteria ◽  
Solid Medium ◽  
Xylanase Activity ◽  
Relative Activity ◽  
Optimum Activity ◽  
Ph Values ◽  
Xylan Hydrolysis ◽  
Pure Cultures ◽  
The Stability

This work aimed to evaluate a collection of common and rare soil bacteria regarding to extracellular xylanases production and to characterize the stability in contrasting conditions of temperature and pH of these enzymes. This collection consists of 120 isolates belonging to six phyla that were subjected to screening for xylanase activity in pure cultures and in the extracellular proteic extract (EPE). The ratio between the halos diameters of xylan hydrolysis and in the colonies on solid medium (ratio H:C) was used for the evaluation of cultures as selection criteria. EPEs of isolates with highest ratios H:C were evaluated for the specific xylanases activity at 50 °C for 1 h. EPE of the three isolates with the highest potential for activity under this condition were evaluated for optimum activity, stability at 60 °C and different pH values. Twenty-two isolates showed xylanase activity under these conditions. Xylanases from TC21 and TC119 showed high relative activity at temperatures up to 70 °C and were less sensitive to changes in pH. Soil bacteria show high potential as a source of extracellular xylanases adapted to extreme pH and temperature conditions, which are required in agroindustrial processes.

Ascospore germination, growth in culture, and imperfect spore formation in Cookeina sulcipes and Phillipsia crispata

1975 ◽  
Vol 53 (1) ◽  
pp. 56-61 ◽  
Author(s):  
J. W. Paden
Keyword(s):  
Germ Tube ◽  
Outer Wall ◽  
Wall Layer ◽  
Spore Formation ◽  
Spore Surface ◽  
No Formation ◽  
Ascospore Germination ◽  
Germ Tubes

Ascospores of Cookeina sulcipes germinate by one of two modes: (1) by the production of blastoconidia on sympodially proliferating conidiogenous cells which may arise from any point on the spore surface, and (2) by a thick polar germ tube. No ascospores were seen to germinate both ways. The conidiogenous cells are occasionally modified into narrow hyphae. The blastoconidia germinate readily but are evidently very short-lived. Ascospores of Phillipsia crispata germinate by two polar germ tubes; there is no formation of blastoconidia. In both species the inner ascospore wall separated from an outer wall layer during germination. In culture both C. sulcipes and P. crispata form arthroconidia. The arthroconidia are uninucleate; they germinate readily and reproduce the species when transferred to fresh plates.

Carbon dioxide induces endotrophic germ tube formation in Candida albicans

1990 ◽  
Vol 36 (4) ◽  
pp. 249-253 ◽  
Author(s):  
Ruth C. Mock ◽  
Jordan H. Pollack ◽  
Tadayo Hashimoto
Keyword(s):  
Carbon Dioxide ◽  
Candida Albicans ◽  
Sodium Bicarbonate ◽  
Key Words ◽  
Germ Tube ◽  
Tube Formation ◽  
Chemical Inducers ◽  
Tube Emergence ◽  
Ph Range ◽  
Germ Tubes

Candida albicans formed germ tubes when exposed to air containing 5 to 15% carbon dioxide (CO2). The CO2-mediated germ tube formation occurred optimally at 37 °C in a pH range of 5.5 to 6.5. No germ tubes were produced at 25 °C, even when the optimal concentration of CO2 (10%) was present in the environment. The requirement of CO2 for germ tube formation could be partially substituted by sodium bicarbonate but not by N2. Carbon dioxide was required to be present throughout the entire course of germ tube emergence suggesting that its role is not limited to an initial triggering of morphogenic change. We suggest that carbon dioxide may be a common effector responsible for the germ tube promoting activity of certain chemical inducers for C. albicans. Key words: Candida albican germ tubes, CO2-induced germ tube formation, endotrophic germ tube formation.

Behavior of zoospores of Phytophthora megasperma var. sojae and P. drechsleri in soil

1972 ◽  
Vol 50 (11) ◽  
pp. 2125-2130 ◽  
Author(s):  
R. S. Mehrotra
Keyword(s):  
Fluorescence Microscope ◽  
Natural Soil ◽  
Moderate Degree ◽  
Percentage Germination ◽  
Phytophthora Megasperma ◽  
Potential Capacity ◽  
Perfusion Apparatus ◽  
Phytophthora Drechsleri ◽  
Germ Tubes ◽  
Modified Soil

Experiments done with the modified soil perfusion apparatus indicate the potential capacity of the zoospores and cysts of Phytophthora drechsleri and P. megasperma var. sojae as inoculum units in soil. The results indicate that although zoospores/cysts do not retain infectivity for months, those of P. drechsleri do not lose it very rapidly. Experiments done to find out the period of motility of zoospores have shown that some zoospores of P. drechsleri and P. megasperma var. sojae remained motile for up to 30 and 24 h respectively. Saprophytic behavior of the two species of Phytophthora has been studied with the help of a fluorescence microscope and using a fluorescent dye. Cysts of P. drechsleri and P. megasperma var. sojae germinate to a moderate degree in natural non-amended soil. Germination ranged from 30 to 50% in the case of P. drechsleri and 15 to 25% in P. megasperma var. sojae. Amending the soil with 0.4% glucose, 0.4% asparagine increased the percentage germination of cysts in natural soil. Germ tubes of a small percentage of cysts in the two species terminate in miniature sporangia-like structures.

scholarly journals Regulation of Pathogenic Spore Germination by CgRac1 in the Fungal Plant Pathogen Colletotrichum gloeosporioides

2011 ◽  
Vol 10 (8) ◽  
pp. 1122-1130 ◽  
Author(s):  
Iris Nesher ◽  
Anna Minz ◽  
Leonie Kokkelink ◽  
Paul Tudzynski ◽  
Amir Sharon
Keyword(s):  
Cell Division ◽  
Plant Pathogen ◽  
Germ Tube ◽  
Colletotrichum Gloeosporioides ◽  
Fluorescent Protein ◽  
Nuclear Division ◽  
Simultaneous Formation ◽  
Content Type ◽  
Germ Tubes

ABSTRACT Colletotrichum gloeosporioides is a facultative plant pathogen: it can live as a saprophyte on dead organic matter or as a pathogen on a host plant. Different patterns of conidial germination have been recognized under saprophytic and pathogenic conditions, which also determine later development. Here we describe the role of CgRac1 in regulating pathogenic germination. The hallmark of pathogenic germination is unilateral formation of a single germ tube following the first cell division. However, transgenic strains expressing a constitutively active CgRac1 (CA-CgRac1) displayed simultaneous formation of two germ tubes, with nuclei continuing to divide in both cells after the first cell division. CA-CgRac1 also caused various other abnormalities, including difficulties in establishing and maintaining cell polarity, reduced conidial and hyphal adhesion, and formation of immature appressoria. Consequently, CA-CgRac1 isolates were completely nonpathogenic. Localization studies with cyan fluorescent protein (CFP)-CgRac1 fusion protein showed that the CgRac1 protein is abundant in conidia and in hyphal tips. Although the CFP signal was equally distributed in both cells of a germinating conidium, reactive oxygen species accumulated only in the cell that produced a germ tube, indicating that CgRac1 was active only in the germinating cell. Collectively, our results show that CgRac1 is a major regulator of asymmetric development and that it is involved in the regulation of both morphogenesis and nuclear division. Modification of CgRac1 activity disrupts the morphogenetic program and prevents fungal infection.

Emergence of the aeciospore germ tubes of Cronartium coleosporioides (=Peridermium stalactiforme) as observed by scanning electron microscope

1970 ◽  
Vol 48 (9) ◽  
pp. 1692-1692 ◽  
Author(s):  
Y. Hiratsuka
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Germ Tube ◽  
Germ Tubes ◽  
Scanning Electron

Germ tubes of Cronartium coleosporioides Arth. (= Peridermium stalactiforme Arth. and Kern) emerged between processes through short irregular slits. Germ tube walls were folded when they emerged and expanded after the emergence.

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