Bacteria and Crew Health Issues

ASEN 5016 Lecture 26: Microbes and Related Crew Health Issues

OBJECTIVES

1. Describe general characteristics of microorganisms, bacteria in particular

2. Discuss background of bacterial space flight research

3. Summarize of space flight effects on bacteria

4. Describe theories of underlying physical mechanisms

5. Identify crew health implications

Characteristics of microorganisms

Organisms invisible to the unaided human eye

· Less than ~ 0.002 inch (50 mm) diameter

· Smallest of which are single-celled organisms

Eukaryotes – fungi, protozoa and most algae (higher protists)

Prokaryotes –bacteria and blue-green algae (lower protists)

(Note that viruses are different, somewhere in between living and non-living systems)

General information on bacteria

· On the order of 1-5 mm

· Growth kinetics – lag, exponential growth, stationary, (sporulation), death

· Can be motile or non-motile, aerobic or anaerobic

· Uptake nutrients and produce metabolic by-products

· Can produce antimicrobial substances (antibiotics)

· Killed by antibiotics (class of antimicrobials)

· Can develop resistance to antibiotics

· Can cause disease (pathogenic, virulence)

Summary of space flight effects on Bacteria

· Shortened lag phase

· "Possibly" slower growth rate and longer exponential phase

· Higher final population concentrations

· Higher concentration of antibiotic needed to inhibit growth

· Increased virulence

· Increased specific productivity of antibiotics

· More efficient cell mass yield

· None of the above…

· How can gravity influence all of the above???

Underlying physical mechanisms

· Physical factors to be considered?

· What are the gravity-dependent forces that affect bacterial growth?

· Direct vs. indirect effects (remember deformation or displacement)

· Clinostat (and other analog) experiments show similar trends

· Related crystal growth theory

· Other microbes

Crew Health Implications

· Enhanced microbial growth

· Microflora exchange in a closed environment

· Immunosuppression (?)

· Increased antibiotic resistance / Decreased antibiotic effectiveness (?)

· Increased virulence

· Altered Pharmacokinetics

· Shelf life reduction (?)

Rapid enumeration / identification technologies needed onboard spacecraft

Studies needed to determine effective drug dosage and administration regimen

Health care systems must ultimately address increasingly long duration missions without intervention from Earth