Pink Erwinia amylovora: Colony discoloration in diagnostic isolations by co-cultured bacteria

V. O. Stockwell, Kevin Hockett, C. Mane, B. Duffy

Research output: Contribution to journalConference article

4 Citations (Scopus)

Abstract

Accurate diagnosis of fire blight from plant samples relies on characteristic colony appearance of Erwinia amylovora on isolation media. We found that diagnosis is occasionally hindered due to a pink coloration of pathogen colonies on plates with mixed cultures. When these pink colonies were streaked to purity, E. amylovora reverted to typical white mucoid colonies on King's medium B. However, E. amylovora rapidly develops a vivid pink color when streaked adjacent to, but not in contact with, phyllosphere epiphytes Erwinia persicina or Erwinia rhapontici. These bacteria had no inhibitory activity against E. amylovora in vitro. Laboratory assays with E. persicina indicate that it produces a non-volatile, color-changing metabolite, which is accumulated by E. amylovora. Cell-free extracts from E. persicina cultures caused an identical pink coloration in E. amylovora. The colorless extracts developed an intense pink color upon addition of iron. The absorption spectrum of the ferrated extract had a major peak at 556 nm and a shoulder at 510 nm characteristic of the iron (II) chelator proferrorosamine (pFR). Diffusion of pFR in agar from E. persicina was visible only in media containing iron; otherwise the pink coloration was only seen in colonies. Our findings demonstrate that although E. persicina or E. rhapontici do not inhibit growth of E. amylovora in vitro, the pathogen's absorption of the pFR they secrete, poses a concern in diagnostics because atypical colony-color can lead to pathogen misidentification.

Original languageEnglish (US)
Pages (from-to)539-542
Number of pages4
JournalActa Horticulturae
Volume793
DOIs
StatePublished - Jan 1 2008
Event11th International Workshop on Fire Blight - Portland, OR, United States
Duration: Aug 12 2007Aug 17 2007

Fingerprint

Erwinia persicina
Erwinia amylovora
discoloration
bacteria
color
Erwinia rhapontici
iron
pathogens
extracts
phyllosphere
epiphytes
mixed culture
chelating agents
shoulders
purity
agar
metabolites
assays

All Science Journal Classification (ASJC) codes

  • Horticulture

Cite this

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title = "Pink Erwinia amylovora: Colony discoloration in diagnostic isolations by co-cultured bacteria",
abstract = "Accurate diagnosis of fire blight from plant samples relies on characteristic colony appearance of Erwinia amylovora on isolation media. We found that diagnosis is occasionally hindered due to a pink coloration of pathogen colonies on plates with mixed cultures. When these pink colonies were streaked to purity, E. amylovora reverted to typical white mucoid colonies on King's medium B. However, E. amylovora rapidly develops a vivid pink color when streaked adjacent to, but not in contact with, phyllosphere epiphytes Erwinia persicina or Erwinia rhapontici. These bacteria had no inhibitory activity against E. amylovora in vitro. Laboratory assays with E. persicina indicate that it produces a non-volatile, color-changing metabolite, which is accumulated by E. amylovora. Cell-free extracts from E. persicina cultures caused an identical pink coloration in E. amylovora. The colorless extracts developed an intense pink color upon addition of iron. The absorption spectrum of the ferrated extract had a major peak at 556 nm and a shoulder at 510 nm characteristic of the iron (II) chelator proferrorosamine (pFR). Diffusion of pFR in agar from E. persicina was visible only in media containing iron; otherwise the pink coloration was only seen in colonies. Our findings demonstrate that although E. persicina or E. rhapontici do not inhibit growth of E. amylovora in vitro, the pathogen's absorption of the pFR they secrete, poses a concern in diagnostics because atypical colony-color can lead to pathogen misidentification.",
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Pink Erwinia amylovora : Colony discoloration in diagnostic isolations by co-cultured bacteria. / Stockwell, V. O.; Hockett, Kevin; Mane, C.; Duffy, B.

In: Acta Horticulturae, Vol. 793, 01.01.2008, p. 539-542.

Research output: Contribution to journalConference article

TY - JOUR

T1 - Pink Erwinia amylovora

T2 - Colony discoloration in diagnostic isolations by co-cultured bacteria

AU - Stockwell, V. O.

AU - Hockett, Kevin

AU - Mane, C.

AU - Duffy, B.

PY - 2008/1/1

Y1 - 2008/1/1

N2 - Accurate diagnosis of fire blight from plant samples relies on characteristic colony appearance of Erwinia amylovora on isolation media. We found that diagnosis is occasionally hindered due to a pink coloration of pathogen colonies on plates with mixed cultures. When these pink colonies were streaked to purity, E. amylovora reverted to typical white mucoid colonies on King's medium B. However, E. amylovora rapidly develops a vivid pink color when streaked adjacent to, but not in contact with, phyllosphere epiphytes Erwinia persicina or Erwinia rhapontici. These bacteria had no inhibitory activity against E. amylovora in vitro. Laboratory assays with E. persicina indicate that it produces a non-volatile, color-changing metabolite, which is accumulated by E. amylovora. Cell-free extracts from E. persicina cultures caused an identical pink coloration in E. amylovora. The colorless extracts developed an intense pink color upon addition of iron. The absorption spectrum of the ferrated extract had a major peak at 556 nm and a shoulder at 510 nm characteristic of the iron (II) chelator proferrorosamine (pFR). Diffusion of pFR in agar from E. persicina was visible only in media containing iron; otherwise the pink coloration was only seen in colonies. Our findings demonstrate that although E. persicina or E. rhapontici do not inhibit growth of E. amylovora in vitro, the pathogen's absorption of the pFR they secrete, poses a concern in diagnostics because atypical colony-color can lead to pathogen misidentification.

AB - Accurate diagnosis of fire blight from plant samples relies on characteristic colony appearance of Erwinia amylovora on isolation media. We found that diagnosis is occasionally hindered due to a pink coloration of pathogen colonies on plates with mixed cultures. When these pink colonies were streaked to purity, E. amylovora reverted to typical white mucoid colonies on King's medium B. However, E. amylovora rapidly develops a vivid pink color when streaked adjacent to, but not in contact with, phyllosphere epiphytes Erwinia persicina or Erwinia rhapontici. These bacteria had no inhibitory activity against E. amylovora in vitro. Laboratory assays with E. persicina indicate that it produces a non-volatile, color-changing metabolite, which is accumulated by E. amylovora. Cell-free extracts from E. persicina cultures caused an identical pink coloration in E. amylovora. The colorless extracts developed an intense pink color upon addition of iron. The absorption spectrum of the ferrated extract had a major peak at 556 nm and a shoulder at 510 nm characteristic of the iron (II) chelator proferrorosamine (pFR). Diffusion of pFR in agar from E. persicina was visible only in media containing iron; otherwise the pink coloration was only seen in colonies. Our findings demonstrate that although E. persicina or E. rhapontici do not inhibit growth of E. amylovora in vitro, the pathogen's absorption of the pFR they secrete, poses a concern in diagnostics because atypical colony-color can lead to pathogen misidentification.

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