Pseudomonas syringae

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Pseudomonas syringae
Scientific classification
Kingdom: Bacteria Phylum: Proteobacteria Class: Gamma Proteobacteria Order: Pseudomonadales Family: Pseudomonadaceae Genus: Pseudomonas Species: P. syringae
Binomial name
Pseudomonas syringae Van Hall, 1904

Pseudomonas syringae is a rod shaped, Gram-negative bacterium, with polar flagella. It is a plant pathogen which can infect a wide range of plant species, and exists as over 50 different pathovars. Many of these pathovars were once considered to be individual species within the Pseudomonas genus, but molecular biology techniques such as DNA hybridization have shown these to in fact all be part of the P. syringae species. It is named after the lilac tree (Syringa vulgaris), from which it was first isolated^[1]. The type strain is ATCC 19310.

P. syringae tests negative for arginine dihydrolase and oxidase activity, and forms the polymer levan on sucrose nutrient agar. It is known to secrete the lipodepsinonapeptide plant toxin syringomycin,^[2] and it owes its yellow fluorescent appearance when cultured in vitro on King's B medium to production of the siderophore pyoverdin.^[3] It also demonstrates ice nucleating properties.^[4]

Contents 1 Epidemiology 2 Pathovars 3 Genome sequencing projects 4 References

[edit] Epidemiology

Disease by P. syringae tends to be favoured by wet, cool conditions - optimum temperatures for disease tend to be around 55 to 77 degrees farenheit, although this can vary according to the pathovar involved. The bacteria tend to be seed borne, and are dispersed between plants via rain splash.^[5].

Although it is a plant pathogen, it can also live as a saprophyte in the phyllosphere when conditions are not favourable for disease.^[6] Some saprophytic strains of P. syringae have been used as biocontrol agents against post-harvest rots^[7].

[edit] Pathovars

The principle pathovars of P. syringae of economic importance are as follows:^[8]

Pathovar	Main host and disease caused
antirrhini	Blight of antirrhinum
aptata	Affects sugar beet
atrofaciens	Affects wheat and barley
avellanae	Affects hazelnut
cannabina	Leaf and stem spot of hemp
coronofaciens	Halo blight of oats
glycinea	Bacterial blight of soybean
helianthi	Angular leaf spots on sunflower
lachrymans	Curcubit angular leaf spot and fruit spot
maculicola	Brassica bacterial spot
mori	Mulberry leaf spot and shoot blight
morsprunorum	Affects cherry, plum and other stone fruit trees
persicae	Affects peaches and nectarines
phaseolicola	Affects runner beans
pisi	Affects peas
porri	Affects leeks
syringae	Affects a very wide range of host plants
tabaci	Wildfire disease of tobacco
tagetis	Affects African marigold
tomato	Bacterial speck of tomato
ulmi	Leaf spot and shoot blight of elm

Note that Pseudomonas syringae ssp. savastanoi (previously called Pseudomonas savastanoi) is a sub-species of P. syringae rather than a pathovar. It itself has three host-specific pathovars, fraxini which causes ash canker, nerii which attacks oleander and oleae which causes olive knot.

[edit] Genome sequencing projects

The genomes of several strains of P. syringae have been sequenced, including P. syringae pv. tomato DC3000, P. syringae pv. syringae B728a and P. syringae pv. phaseolicola 1448A.^[9]

[edit] References