The use of genetic approaches to study bacteria is limited by the following considerations: first, the bacteria must be easy to culture and nonpathogenic; and, second, a broad spectrum of genetic techniques for the particular bacteria being studied must be available. For other bacteria, such as the syphilis-causing spirochete, Treponema pallidum, genetic studies are highly limited because the bacterium cannot be continuously grown in the laboratory, because of its high virulence and a total lack of genetic tools to study this organism.