Spirochetes (Family Spirochaeteae)

• Unique morphology & cork screw motility
• Aerobic, microaerophilic or anaerobic
• Some culturable, some pathogenis others saprophytic
• Some ferment or oxidise sugars or fatty acids
• RNApolymerase insensitive to rifampin & incorporated in growth culture medium for selection.

• Helical cells (protoplasmic cylinders, PC)
• Trilayered membrane outer sheath (OS)
• Axial filaments or periplasmic fibrils (PF)
  • Structure (rings, hook & basal body) and chemistry similar to bacterial flagella.
  • PF wound between OS & PC two-thirds of PC on either ends
  • 2-100 PF depending on spirochete species
  • PF on either ends rotate in opposite directions--cork screw motility

• Cristispira: Giant spirochetes (10um width); symbiotic in clams & oysters; uncultured.

• Spirochaete:
  • Free-living anaerobes; ferement sugars to acetate, ethanol, CO2 and H2
    OR
    
  • Free-living aerobes; oxidise sugars to acetate and CO2; Aquatic habitat.

• Treponema: Host associated commensals or parasites of humans & animals; anaerobic;
  • T. pallidum-- STD syphilis; infects male genital organs; cooling of infected region decreases infection (heat sensitive, 41 C); treatment antibiotics; remains uncultured; identified in patient exudates by special silver staining (thin cells).

• Borrelia: Host assosiated parasite; Anaerobic to microaerophilic; culturable on complex artificial medium; Thick cells & identified by normal staining
  • B. recurrentis-- relapsing fever in humans; 2 or 3 cycles of 3 - 7 d high fever & muscular pain and recovery for 7 - 9; treatment Tetracycline; Transmission by human body louse (vector transmission)
  • B. Burgdorferi-- (identified in 1975, named after an American town); Lyme disease; transmited by deer ticks to humans; rapid spread due to deer farming; treated by antibiotics; if untreated than arthritis, damage to CNS and cardia failure can occur.

• Leptospira: Obligate aerobes; Simple growth requirements (fatty acids ie lipolytic);
  • L. biflexa-- aquatic & free-living
  • L.interrogans human & animal parasite; host specific eg L. interrogans serovar canicola-- dogs; L. interrogans serovar icteroharrhagiae-- rodents (kideny infected); transmitted to humans via contaminated urine; leptospirosis-- importane cattle disease.