Erwinia carotovora
Adam Guss
Erwinia carotovora is a plant pathogen belonging to the Family Enterobacteriaceae. It is a Gram- negative, rod- shaped bacterium. It is non- sporeforming and peritrichously flagellated. It is a facultative anaerobe and is catalase negative and oxidase positive.

E. carotovora causes death by creating an osmotically fragile cell. It produces extracellular pectic enzymes that destroy the integrity of the pectin. To a lesser extent, it produces an extracellular cellulase to degrade cellulose. Other exported enzymes thought to be important in pathogenesis include hemicellulases, arabanases, xylanases and a protease.  Other common soil bacteria such as Bacillus spp., Clostridium spp., and Pseudomonas spp. have been shown to produce these same enzymes under ideal conditions in vitro, but do not seem to produce these symptoms in the field except under extreme conditions.

Much debate has centered around the classification of the genus Erwinia.  Originally, the whole genus was created based on phytopathogenic traits.  Many who have worked with the genus, however, have suggested making it into at least two distinct genera or moving some to other existing genera.  For a period, E. carotovora was placed in Pectobacterium along with the other pectolytic phytopathogenic Erwinia, but based on DNA homology and “numerical taxonomy”1, the original classification has been reinstated.

Modes of transport are quite varied. One is plant to plant infection. Most potato seed tubers have some form of soft rot Erwinia on their skin from the mother tuber rotting. Upon injury to the tuber, the infection takes over and quickly rots the tuber. Often, this takes many others with it, especially in industrial harvesting, where a large quantity would be exposed to a rotting tuber. Many insects are also carriers. E. carotovora can survive in an insect’s gut for several hours and therefore can easily be transferred from plant to plant this way.

Another mode of transport is via aerosols. When rain falls on either diseased plants or any other thing that is contaminated with Erwinia, an aerosol can be created where the bacteria is airborne in water. Around 50% can only survive as an aerosol for 5- 10 minutes, but this is long enough to travel many miles in a brisk wind.  It has also recently been shown that E. carotovora can be found in water. It has been found “in surface waters, streams, rivers, lakes, reservoirs, ditches, and the sea in many countries.”2  It is speculated that these organisms became introduced to the water via aerosols, runoff into rivers, and dumping of rotten potatoes. Whether E. carotovora can survive in the soil has yet to be determined.

Works Cited:
1.  Perombelon, Michael CM. The Prokaryotes.  Second Edition. p2899.
2.  Perombelon, Michael CM. The Prokaryotes.  Second Edition. p2909.

References:
1.  Perombelon, Michael CM. The Prokaryotes.  Second Edition. p2899- - 2921.

*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.

 

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