Bacteria: Kingdom Prokaryotae (Monera)

• No organized nucleus

• Single-celled organisms; are ubiquitous in nature

• Amplification (growth) by an increase in number of cells, not by an increase in size

• Can demonstrate classic exponential growth

Ex: Legionella pneumophila, (a gram-negative, aerobic bacillus) responsible for Legionnaires’ disease, Pontiac fever

• Cooling towers, fountains, hot tubs, building water systems

• See ASHRAE Guideline 12-2000:  Minimizing the Risk of Legionellosis Associated with Building Water Systems

Other Gram-negative bacilli (rod-shaped)

• Endotoxin: cell wall component

• Heat-stable molecule – not eliminated by autoclaving

• Highly toxic: Gram-negative bacterial infection produces fever, malaise, changes in white blood cell counts, respiratory distress, shock

• Acute and chronic inhalation effects include airflow obstruction, accelerated loss of lung function

Gram-positive bacilli

• Prevalent in soil, water, air and vegetation

• Spore-bearing; spores resistant to environmental stress

• Most are non-pathogenic (do not cause disease)

  • Exception: Bacillus anthracis, responsible for anthrax

    • Spores are 1 - 1.5 microns in size

    • Transform into reproducing bacilli in chest lymph nodes

    • Release toxins that cause septic shock and respiratory failure

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