Cells are the fundamental building block for all living organisms. The word cells was first coined by physicist Robert Hooke during his examination of a cork slice under a microscope. Complex organisms such as plants and animals are made of many cells that work together. Microorganisms are single cell organisms that are too small to see with the naked eye. Microorganisms were first discovered with the invention of a microscope by the Dutch scientist Anton van Leeuwenhoek. Leeuwenhoek, who made microscopes to count threads in drapery material for his shop in Holland, first described microorganisms as animalcules or little animals. Improvements in microscopes have greatly increased the knowledge of microorganisms and have led to many advances in medicine. However, much is still to be learned about the biological processes of microorganisms. The objective of this experiment was to determine the effects of microgravity on the survival, growth rates, and mutations of certain bacteria and spores.
During Skylab 2, colonies of E. coli did not develop and 75 colonies of B. subtilis developed following inflight inoculation. Bacteria growth rate was slower than expected for the flight cultures, therefore, the incubation time was extended from 48 hours to 69 hours. In addition, the ground control colonies also experienced a slower than expected growth rate. This experiment was repeated on Skylab 4 with B. mycoides substituted for E. coli. However, B. mycoides, like E. coli, failed to grow colonies on Skylab 4. The slower-than-planned growth rate of both flight and ground control colonies was also observed on Skylab 4. In addition, it was observed that there was contamination in the Petri dishes. Overall, bacterial control cultures grew more colonies compared to the Skylab cultures. However, the colonies that grew on Skylab were larger, grew faster, and were more irregular than control colonies. On Skylab 2, B. subtilis colonies were 50 percent larger than control colonies. Individual cells grew larger in diameter, but did not significantly increase in number. In addition, Skylab grown bacteria appeared to be more sensitive to postflight antibiotic treatment.