Plant Diseases – Bacteria

For the next several posts, I’m taking a look at diseases that affect plants in the San Francisco Bay Area, specifically in the Monera (bacteria) Super kingdom. For sources I’m using FiveKingdoms, Essential Plant Pathology, the U.C. Davis Integrated Pest Management (IPM) website, and information from my plant diseases course at Merritt College in Fall 2012.

Bacteria are categorized as prokaryotes; they have small ribosomes surrounding their nucleoids, but lack a surrounding membrane. Bacteria are small, and live in large colonies that can grow unchecked if conditions are favorable. Genes are organized into thin fibrils, and are passed from one cell to another. Scientists have recently discovered that bacteria communicate chemically. They can live in relative isolation, but participate in a phenomenon known as quorum sensing – when they sense chemically they have enough numbers, they may take action as a group. Learn more: http://www.ted.com/talks/bonnie_bassler_on_how_bacteria_communicate.html

Bacteria are hardy, and can survive in extreme conditions. They move in water, and invade plants through natural opening, such as stomata, or through damaged tissue. Bacteria are dispersed through sticky masses. Bacteria are typically spherical (cocci), rod shaped, or spiral shaped, so, to identify them, you need to test for chemical changes rather than simply observe them under the microscope. Bacteria are critical to healthy soil, and most are not pathogenic.

With our dry, Mediterranean climate, the San Francisco Bay Area does not suffer from many bacterial plant diseases. However, with our wet, rainy season, temperate climate, and coastal fog, we do have conditions part of the year that are favorable to bacteria.