scholarly journals Ultrastructure, Morphology, and Sporogenesis of Pasteuria penetrans

1997 ◽  
Vol 87 (3) ◽  
pp. 273-283 ◽  
Author(s):  
Z. X. Chen ◽  
D. W. Dickson ◽  
L. G. Freitas ◽  
J. F. Preston

Pasteuria penetrans is a bacterial parasite of root-knot nematodes that shows great potential as a biocontrol agent. Scanning and transmission electron microscopy were used to study the ultrastructure, morphology, and sporogenesis of four isolates of P. penetrans. The effects of different Meloidogyne spp. and tobacco cultivars on sporangium size and morphology of endospores attached to the cuticle of second-stage juveniles (J2) of root-knot nematodes also were investigated. The P. penetrans isolates and their origins were P-20 from M. arenaria race 1 in Levy County, FL; P-100 from Meloidogyne sp. in Pasco County, FL; B-4 from Pratylenchus scribneri in Seminole County, FL; and P-120 from Meloidogyne spp. in Alachua County, FL. Sporangia of the four isolates were identical morphologically and similar in their dimensions, ranging from 2.39 to 3.42 μm in diameter and from 1.38 to 2.38 μm in height. Different Meloidogyne spp. and tobacco cultivars had no effect on sporangium size. Endospores attached to J2 were visualized in three forms: endospores retaining the sporangium wall, endospores covered with a thin exosporium, and endospores without covering. Sporogenesis of P. penetrans was similar to that of other gram-positive bacteria and generally matched the seven-stage scheme reported for Bacillus thuringiensis.

Nematology ◽  
1999 ◽  
Vol 1 (3) ◽  
pp. 267-271 ◽  
Author(s):  
Regina M.D.G. Carneiro ◽  
Onivaldo Randig ◽  
Leandro G. Freitas ◽  
Don W. Dickson

Abstract The attachment of endospores to Meloidogyne spp. males and second stage juveniles (J2) was evaluated in two different in vitro assays of seven isolates of Pasteuria penetrans from Florida, USA. In the first assay, endospores of all seven isolates adhered to J2 but not males of M. arenaria race 1. In the second assay, two isolates differed in the specificity of spore attachment to J2 of six Meloidogyne spp. Isolate B4, from Pratylenchus scribneri, showed a similar degree of attachment to J2 of M. arenaria race 2, M. javanica (two populations) and to M. incognita race 3, but did not attach to males of seven species. Isolate P100, from Meloidogyne sp., had high rates of attachment to M. javanica from Rio Grande do Sul State and to M. paranaensis, but lower rates to M. arenaria and M. javanica from Parana State. These data indicate that attachment ability depends not only on the Meloidogyne species but also on the particular population of a species. The high rate of attachment to male but not J2 M. hapla indicates that endospore attachment may also depend upon nematode stage, species, race and population and on Pasteuria isolate. Germinated endospores attached to male M. hapla were examined by scanning electron microscopy but few had successfully penetrated the cuticle. Adhesion des endospores de Pasteuria penetrans aux males et juveniles de Meloidogyne spp. - L'adhesion des spores de Pasteuria penetrans aux males et juveniles de deuxieme stade (J2) de Meloidogyne spp. a ete evaluee lors de deux differents tests in vitro comprenant sept isolats de P. penetrans provenant de Floride, USA. Lors du premier test les endospores des sept isolats ont adhere aux J2 mais non aux males de M. arenaria race 1. Lors du second test deux isolats se sont distingues quant a la specificite de l'adhesion de leurs spores aux J2 de six des especes de Meloidogyne. L'isolat B4, provenant de Pratylenchus scribneri, montre un taux d'adhesion similaire vis-a-vis des J2 de M. arenaria race 2, M. javanica (deux populations) et M. incognita race 3, mais n'adhere aux males d'aucune des sept especes. L'isolat P 100, provenant de Meloidogyne sp., Montre un taux d'adhesion eleve vis-a-vis tant de M. javanica provenant de l'Etat de Rio Grande del Sul que de M. paranensis mais ce taux est faible vis-a-vis de M. arenaria et M. javanica originaires de l'Etat du Parana. Ces donnees indiquent que la faculte d'adhesion depend non seulement de l'espece de Meloidogyne en cause mais egalement de la population particuliere de cette espece. Le taux eleve d'adhesion vis-a-vis des males, mais non des J2, de M. hapla indique que cette adhesion peut dependre du stade de developpement du nematode, de son espece, race ou population ainsi que de l'isolat lui-meme de P. penetrans. Les endospores fixees aux males de M. hapla, et ayant germe, ont ete examinees en microscopie electronique a balayage: peu d'entre elles avaient reussi a traverser la cuticule.


Nematology ◽  
2012 ◽  
Vol 14 (7) ◽  
pp. 799-804 ◽  
Author(s):  
Uma Rao ◽  
Tim H. Mauchline ◽  
Keith G. Davies

The molecular interactions between hosts and parasites is an active area of research, and the parasitism of root-knot nematodes, obligate parasites of plants, by the hyper-parasitic bacterium Pasteuria penetrans offers a model by which to investigate aspects of innate immunity. Using a pouch system we were able to demonstrate by PCR, infection of Meloidogyne incognita 4 days prior to any microscopic observations of parasitism. The pouch system, although not strictly axenic, offered a relatively clean, flexible approach with a greatly reduced number of contaminating microbial species than in any soil-based system, whereby the early stages of nematode infection could be manipulated and controlled.


2020 ◽  
Vol 38 (3) ◽  
pp. 239-245
Author(s):  
Jadir B Pinheiro ◽  
Giovani Olegário da Silva ◽  
Danielle Biscaia ◽  
Amanda G Macedo ◽  
Fábio A Suinaga

ABSTRACT Genetic resistance is the most suitable mechanism to control root-knot nematodes in lettuce. However, information about the resistance levels of currently used lettuce cultivars is scarce in the literature. Thus, the objective of this research was to characterize lettuce cultivars for resistance to root-knot nematodes Meloidogyne incognita (Mi) and M. javanica (Mj), aiming the identification of resistance sources for breeding, and to transfer information to the productive sector. We evaluated 97 lettuce genotypes in tree trials. In the first one (preliminary assessment), 92 lettuce genotypes were inoculated simultaneously with M. incognita race 1 and M. javanica species, 17 days after sowing. The gall index (GI) was evaluated 41 days after inoculation. In the second trial nine genotypes, selected from the first trial, were evaluated; and in the third trial, two new cultivars from Embrapa were evaluated. In the last two trials, the nematode species were inoculated separately, and the egg mass index (EMI), number of eggs per gram of roots (NEGR) and reproduction factor (RF) were also evaluated. In both trials, the lettuce cultivars Salinas 88 and Grand Rapids were used as resistant controls, as well as cultivar Irene as the susceptible control. The data were submitted to analysis of variance and treatments means grouping by Scott-Knott´s test. The crisp leaf cultivars presented a higher degree of resistance to the root-knot nematodes compared to the smooth leaf type cultivars. Cultivars Vera and Amanda present resistance to M. incognita, and Vanda to M. javanica. ‘Salinas 88’ present resistance mainly to M. javanica; while cultivar Mônica and the Embrapa cultivars BRS Leila and BRS Mediterrânea are resistant to both nematode species.


Parasitology ◽  
2001 ◽  
Vol 122 (1) ◽  
pp. 111-120 ◽  
Author(s):  
K.G. DAVIES ◽  
M. FARGETTE ◽  
G. BALLA ◽  
A. DAUDI ◽  
R. DUPONNOIS ◽  
...  

The cuticle is a major barrier prohibiting the infection of nematodes against micro-organisms. The attachment of bacterial spores of the nematode hyperparasite Pasteuria penetrans (PP1) to field populations of root-knot nematodes (RKN, Meloidogyne spp.) from Burkino Faso, Ecuador, Greece, Malawi, Senegal and Trinidad and Tobago were assayed in standard attachment tests. The attachment of spore population PP1 to different field populations of root-knot nematode showed that the rates of attachment differed between countries. Similar tests were also undertaken on P. penetrans spores from these countries against 2 species of RKN, M. incognita and M. arenaria. The results showed a high degree of variability in spore attachment with no clear distinction between the 2 species of nematode. It has been hypothesized that Pasteuria spore attachment is linked to nematode species designations and this study clearly shows that this is not the case. Further tests showed that variation in spore attachment was not linked to nematode phylogeny. The results therefore beg the question of how do parthenogenetic root-knot nematodes maintain cuticle variability in the face of such an aggressive hyperparasite.


2002 ◽  
Vol 34 (10) ◽  
pp. 1417-1424 ◽  
Author(s):  
Thierry Mateille ◽  
David L Trudgill ◽  
Carmen Trivino ◽  
George Bala ◽  
Abdoussalam Sawadogo ◽  
...  

2000 ◽  
Vol 620 ◽  
Author(s):  
R. Lee Penn ◽  
Alan T. Stone ◽  
David R. Veblen

ABSTRACTHigh-Resolution Transmission Electron Microscopy (HRTEM) results show a strong crystal-chemical and defect dependence on the mode of dissolution of synthetic heterogenite (CoOOH) particles. As-synthesized heterogenite particles are micron-size plates (aspect ratio ∼ 1/30) constructed of crystallographically oriented ∼ 3-nm primary particles or are single ∼ 21-nm unattached heterogenite platelets (aspect ratio ∼1/7). Reductive dissolution, using hydroquinone, was examined in order to evaluate morphology evolution as a function of reductant concentration. Two end-member modes of dissolution were observed: 1) non-specific dissolution of macroparticles and 2) preferential dissolution along misoriented boundaries. In the case of non-specific dissolution, average macrocrystal size and morphology are not altered as building block crystals are consumed. The result is web-like particles with similar breadth and shape as undissolved particles. Preferential dissolution involves the formation of channels or holes along boundaries of angular misorientation. Such boundaries involve only a few degrees of tilt, but dissolution occurs almost exclusively at such sites. Energy-Filtered TEM thickness maps show that the thickness of surrounding material is not significantly different from that of undissolved particles. Finally, natural heterogenite from Goodsprings, Nevada, shows morphology and microstructure similar to those of this synthetic heterogenite.


Sign in / Sign up

Export Citation Format

Share Document