X hits on this document

Word document

SESSION 1 - Discovery - New horizons in plant pathology - page 48 / 65

172 views

0 shares

0 downloads

0 comments

48 / 65

148

Identification and characteristics of saprophytic bacteria associated with populations of Clavibacter michiganensis subsp. sepedonicus in potato tuber samples

Klenová Hana, Kokošková Blanka

Department of Bacteriology, Research Institute of Crop Production, 160 01 Prague, Czech Republic

Clavibacter michiganensis subsp. sepedonicus (Spieckermann & Kotthoff) Davis et al. (Cms), causes bacterial ring rot of potato. Detection and diagnosis of Cms is carried out in accordance with the requirements of EC Directive No. 93/85/EEC based on indirect fluorescent antibody staining (IFAS) and a bioassay with eggplant as the indicator plant. Further diagnostic methods including immunochemical, biochemical and molecular tests are usually used to definitively identify Cms.  A total of 170 non-Cms strains were isolated from tuber samples of potato, ca 2/3 gram-negative and 1/3 gram-positive bacteria. The rate of bacteria cross-reacting with monoclonal antibodies for Cms (Agdia, USA) in immunochemical methods was about 3 %, both in DAS-ELISA (double antibody sandwich enzyme-linked immunosorbent assay) and IFAS. In contrast, the PCR (polymerase chain reaction) test proved to be very specific, because no amplification products were observed with the non-Cms strains. Using the Microbial Identification System BIOLOG, ca 2/3 recovered bacterial strains were identified. Among the Gram-negative bacteria (both aerobic and anaerobic), the strains found most frequently were Pseudomonas fluorescens. Occasional strains of P. syringae, Agrobacterium rhizogenes and Pantoea sp. were found. Among Gram-positive strains, the most frequently isolated were the non-spore-forming rod bacteria Curtobacterium sp., spore-forming rods Bacillus sp., and coccoid bacteria Staphylococcus epidermidis, Micrococcus luteus and Rhodococcus sp. The potential plant-pathogenic bacteria Agrobacterium tumefaciens, Pseudomonas syringae pv. syringae and Xanthomonas vesicatoria were also recovered.

149

Relationship between virulence of strains of Clavibacter michiganesis subsp. sepedonicus and intensity of metabolic activity of several sugars based on the Microbial Identification System BIOLOG

Kokoskova Blanka

Department of Bacteriology, Research Institute of Crop Production, 160 01 Prague, Czech Republic

e-mail: bkokoskova@vurv.cz

Clavibacter michiganensis subsp. sepedonicus (Spieckermann & Kotthoff) Davis et al (Cms) causing ring rot of potato is subject to strict quarantine in several European countries, including the Czech Republic.  Confirmation of the ring rot bacterium in potato tuber samples is primarily based on a bioassay test using eggplants (cv. Black Beauty).  Differences in virulence among Cms strains are evident with the eggplant test. Cms strains with fluidal and non-fluidal colony morphology were tested using the eggplant bioassay and the Microbial Identification System BIOLOG. Monomers, including galactose, glucose, mannose, and ribose were known to be heavily involved in production of extracellular polysaccharides (EPS).  Higher metabolic activity of these particular monomers may be associated with increased virulence among specific Cms strains.  We found that a majority of Cms strains that were highly virulent in the eggplant bioassay also showed stronger metabolic activity of sugars forming EPS than less virulent Cms strains.  However, the correlation was not universal for all strains tested.

150

THE INTERACTION OF TOLAASIN AND WLIP WITH MEMBRANES AS POSSIBLE MECHANISM IN PATHOGENESIS OF MUSHROOMS DISEASES CAUSED BY PSEUDOMONAS TOLAASI AND P. “REACTANS

N.S. IACOBELLIS, P. LO CANTORE, M. DALLA SERRA1, M. CORAIOLA1, G. MENESTRINA1, S. LAZZARONI2 and A. EVIDENTE2

Dipartimento di Biologia, Università degli Studi della Basilicata, Potenza, Italy; 1 ITC &CNR-IBF – Unit in Trento, Italy; 2Dipartimento di Scienze del Suolo, Pianta e Ambiente, Università di Napoli “Federico II”, Italy. (e-mail: iacobellis@unibas.it)

“Brown blotch” of Agaricus bisporus and “Yellowing” of Pleurotus ostreatus, mushrooms diseases known to be caused by Pseudomonas tolaasii, have been recently shown to be complex diseases. In fact, besides P. tolaasii also other bacteria including P. “reactans” are responsible of the symptom development on the hosts. Furthermore, P. “reactans”, a bacterial entity not yet classified and known in bibliography for its use in the “white line” assay for the specific identification of P. tolaasii, has been determined to be the casual agent of the “Yellowing” of P. eryngii. Virulent strains of P. tolaasii produce in culture an extracellular lipodepsipeptide (LDP) called tolaasin I which is considered the main virulence factor of the pathogen. In fact, it has been reported that tolaasin I has antifungal activity and this is apparently due to the ability of this molecule to disrupt cell membrane function by the transmembrane pore formation. Also P. “reactans” produces a lipodepsipeptide called the “White Line Inducing Principle” (WLIP), which is known for its ability to interact with tolaasin I and form a white precipitates in the “white line” assay, but not yet characterised for the biological activities and for its possible role in the disease development. The fact that avirulent variants of the latter pathogen have been demonstrated to lack also the WLIP production prompt us to characterise it also in comparison to tolaasin I. Antimicrobial assays showed that tolaasin I and WLIP  inhibited the growth of filamentous fungi and yeasts as well as Gram-positive bacteria. Only a limited activity was observed toward some Gram-negative bacteria. Of particular interest is the activity of tolaasin I and WLIP toward the growth of the cultivated mushrooms Agaricus bisporus, Lentinus edodes and Pleurotus spp.. Assays of the two LDPs on blocks of A. bisporus confirmed their

Document info
Document views172
Page views172
Page last viewedSun Dec 11 06:43:08 UTC 2016
Pages65
Paragraphs971
Words49945

Comments