2Virulence Factors Bacterial Colonization 1. adhere to host cells and resist physical removal2. contact host cells3. invade host cells4. resist innate immune defenses such as phagocytosis5. evade adaptive immune defenses6. compete for iron and other nutrients
3Fastidious Bacteria Characteristics: 1. Bacilli The term fastidious refers to the difficulty of obtaining pure cultures of bacterium, due to special medium requirements, slow growth, etc. "Fastidious" = fussy, meticulous.Characteristics:1. Bacilli2. No flagellae (non-motile)3. Most are Gm -, except for Clavibacter (Gm +) - causal agent for ratoon stunt disease (RSD) of sugarcane, bermudagrass stunt.4. Sensitivity to high temperatures - hot air and water treatments can kill them. Ex: RSD in sugarcane. Good control is hot water treatment of seed cane.
4FASTIDIOUS BACTERIA Two Basic Groups: Phloem limited - Can't be grown in pure culture. Ex: citrus greening
5FASTIDIOUS BACTERIA Two Basic Groups: Phloem limited - Can't be grown in pure culture. Ex: citrus greening2. Xylem limited - can be grown in pure culture.Ex: 1) Pierce's disease of grape - Xylella fastidiosa2) Ratoon Stunting Disease (RSD) of sugarcane (Leifsonia xyli (formerly Clavibacter xyli subsp. xyli))
6Symptoms of RSD Reddening of tissue General decline of ratooning (stubble crop)Reddening of tissue
7Sugarcane and RSDIn August 2006, 10% of crop is harvested for plantingNitrogen application in Spring ‘07Harvest in the Fall 2007
10PhytoplasmasInitially found to cause a group of diseases called "yellows" diseases.These diseases initially were thought to be caused by viruses because no fungi or bacteria were detected.Essentially they are small, wall-less bacteria.
11Characteristics of Phytoplasmas No cell wall, so they tend to be pleomorphic. They resemble mycoplasmas, which are known animal pathogens. The name "mycoplasma" means "fungus form".2. Specialized three-layered cell membrane instead of a wall.3. Extremely small - can be as small as 125 nm in diameter.4. Can not be grown in pure culture(i.e., no completion of Koch's postulates).5. Fragile, very sensitive to osmotic changes.
12Characteristics of Phytoplasmas 6. Gram -7. Inhibited by antibiotics (i.e., tetracycline) that do not act by disrupting cell wall production (i.e., penicillin).8. Transmitted by insects - leafhoppers (most important), plant hoppers. Piercing-sucking mouthparts! Phytoplasmas actually multiply within the salivary glands of insect vectors.Phytoplasmas are known to cause = 200 plant diseases.Ex: aster yellows, bunchy top of papaya, pear decline, lethal yellowing of palm.
13Website - Phytoplasma Casts A Magic Spell The interactions between a phytoplasma and poinsettia result in dwarfing and moderate branching growth habit, which happens to be a trait that poinsettia growers desire.Technically, free-branching is a disease symptom in poinsettias. But, like the virus associated with classical color-breaking of tulip petals, the poinsettia phytoplasma is beneficial to growers, generating multi-flowered Christmas showpieces and $325 million annually.
14Restricted-branching morphotype Free-branching induced by phytoplasma
16SpiroplasmasSimilar in many regards to phytoplasmas, except that they can be cultured.Characteristics of Spiroplasmas :1. Small, helical organisms. They resemble a corkscrew.2. The are motile. Can somehow use their corkscrew shape to propel themselves.
17SpiroplasmasSimilar in many regards to phytoplasmas, except that they can be cultured.Characteristics of spiroplasmas:1. Small, helical organisms. They resemble a corkscrew.2. The are motile. Can somehow use their corkscrew shape to propel themselves.3. No cell wall.4. Specialized three-layered membrane.5. Exhibit sensitivity to antibiotics that is similar to that for phytoplasmas.Common spiroplasma-induced diseases: Ex: brittle root of horseradish, corn stunt
18Corn Stunt Symptoms are typical of phloem dysfunction: Red leaves, green fruit, leaf dieback, bushy plants, stunting.Disease CycleThe spiroplasma overwinters within the adult leafhopper; when the leafhoppers emerge from overwintering in early spring, they can be infective.Disease symptoms appear about 3 weeksafter the corn is infected.