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Group 5 Facultatively Anaerobic Gram-Negative Rods

By Joan Spencer,2014-11-25 18:41
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Group 5 Facultatively Anaerobic Gram-Negative Rods

    The Erwinia revolution 1

    Group 5 Facultatively Anaerobic Gram-Negative Rods

    The Erwinia revolution

Alphaproteobacteria Rhizobiales Rhizobiaceae (Agrobacterium)

    Sphingomonadales Sphingomonadaceae

    (Rhizomonas)

Betaproteobacteria Burkholderiales Burkholderiaceae (Burkholderia,

    Ralstonia)

     Comamonadaceae (Acidovorax)

     Oxalobacteraceae (Herbaspirillum)

     Genera incertae sedis - (Xylophilus)

    Gammaproteobacteria Pseudomonadales - Pseudomonadaceae

    (Pseudomonas, Rhizobacter)

    Xanthomonadales Xanthomonadaceae

    (Xanthomonas, Xylella)

    Enterobacteriales - Enterobacteriaceae

    (Erwinia, Brenneria,

    Pectobacterium, Pantoea)

Enterobacteriales Gram-negative straight rods. Motile by peritrichous

    flagella or nonmotile. Do not form endospores. Grow in presence or absence

    fo oxygen.

Type genus - Escherichia

    Much of information in this section extracted from:

S. H. De Boer, D. L. Coplin, and A. L. Jones. Erwinia and Pantoea. in: Laboratory rdguide for identification of plant pathogenic bacteria, 3 edition.

Erwinia, Brenneria, Pantoea, and Pectobacterium

Diseases caused by this group

     Soft rot

     Necrotic diseases

    The Erwinia revolution 2

     Wilt diseases

     Galls

     The taxonomic position, nomenclature, and interrelationships of the members of the genus Erwinia have been the subject of diverse proposals. The broadest

    classification is that of Dye (1968, 1969a, 1969b, 1969c), which separates Erwinia into

    the pectolytic soft rot carotovora” group, the yellow pigmented “herbicola” group,

    the white nonpectolytic wilt-causing “amylovora” group, and the “atypical” Erwinia.

    These have turned out to be valid clusterings based on DNA-DNA homology studies and 16S sequence homology (Hauben et al, 1998; Kwon 1997), but do not completely agree with purely phenetic groupings (Verdonck et al, 1987). Controversy remains on whether or not the differences are great enough to constitute new genera. On the basis of 16S rRNA sequence homologies, Hauben et al. (1998) recommended that these four groups be split into the genera Pectobacterium emend, Pantoea gen. nov., Erwinia emend., and

    Brenneria gen. nov., respectively. For now the genus will remain intact with the exception of the group being placed in Pantoea.

     The species and subspecies currently included in the pectolytic soft rot or

    carotovora” group have now been placed in Pectobacterium and include:

    Pectobacterium carotovorum subsp. carotovorum, P. carotovorum subsp. atrosepticma, P.

    carotovorum subsp. betavasculorum, P. carotovorum subsp. wasabiae, P. carotovorum

    subsp. odoriferum, P. chrysanthemi, P. cypripedii, P. rhapontici and P. cacticida.

     The species in the “amylovora” group will be considered together with the atypical erwinias and will include E. amylovora, E. persicina, E. pyrifoliae, E.

    mallotivora, E. psidii, and E. tracheiphila.

E. alni, E. nigrifluens, E. paradisiaca, E. quercina, E. rubrifaciens, and E. salicis (24).

    comprises the species included in the genus Brenneria.

It should be noted that G+C ratios do not entirely support the division of the Erwinia

    species according to the presence or absence of pectolytic abilities, since they suggest a closer similarity between E. amylovora and E. chrysanthemi than between E. amylovora

    and the other species of the “amylovora” group (21). Nevertheless, division of the

    Erwinia genus on the basis of phenotypic characteristics is useful for grouping together those species that require similar protocols for their manipulation within the laboratory.

    The “herbicola” group of yellow pigmented strains which consists of epiphytic

    as well as plant pathogenic bacteria, has now been classified as Pantoea together with

    some species of the genus Enterobacter (12, 16, 18). Initially, Ewing and Fife (1972)

    using DNA-DNA homology data, recommended that Enterobacter agglomerans, E.

    herbicola and E. milletiae be place in E. agglomerans. Gavini et al. in 1989

    recommended that E. agglomerans (including the type species of E. herbicola and E.

    milletiae) be transferred to the new genus Pantoea. Later, E. ananas and E. stewartii

    The Erwinia revolution 3

    were placed into Pantoea. The present genus Pantoea includes the phytopathogens P.

    stewartii, P. ananas, P. citrea and P. agglomerans pvs. milletiae, gypsophilae and

    betae.

     Due to the heterogenity of the genus, a general description of Erwinia is

    necessarily limited. As other members of the family Enterobacteriaceae, the erwinia occur

    as straight rods (0.5-1.0 X 1-3 m) singly, in pairs, or sometimes in short chains, are

    Gram negative and are motile by peritrichous flagella. They are facultatively

    anaerobic, chemoorganotrophic, and grow optimally at 23-30?C. All species are

    oxidase negative but catalase positive; nitrates are not reduced by most species. All

    species catabolize glucose and various other carbohydrates with the production of acid but

    usually without gas formation.

    Much of information in this section extracted from:

De Boer, S. H. and A. Kelman.Erwinia soft rot group. in: Laboratory guide for rdidentification of plant pathogenic bacteria, 3 edition.

Pectobacterium

    The species of the genus Pectobacterium comprise a distinct phylogenetic group as determined by 16S rRNA gene sequence comparisons

A. Erwinia Soft Rot Group

    In 1945 Waldee stated that the soft-rot Erwinia species be placed in a separate genus, Pectobacterium although to date this has not been accepted. Other recommendations to place them in a

    separate genus have lacked support (Mergaert et al, 1984). The soft rot or “carotovora” group

    comprises those species which incite soft rot diseases of plants.

    The following designations are used for the “carotovora” group:

    - Pectobacterium carotovorum subsp. carotovorum * Widely distributed and most

    common

    - P. carotovorum subsp. atrosepticum * Primary cause of blackleg of potatoes.

    - P. carotovora subsp. betavasculorum

    - P. carotovorum subsp. wasabiae

    -