No standardised system exists for differentiating between "B. mallei" and "B. pseudomallei". It is caused by infection with the bacterium "Burkholderia mallei". The Japanese used "B. mallei" in their biological warfare research units. The genome for "B. mallei" is made up of two circular chromosomes. It includes some pathogenic species, such as "Burkholderia mallei" (glanders) and "Burkholderia pseudomallei" (melioidosis). However, the Japanese did not end up creating a biological weapon out of "B. mallei". No vaccine is currently available for humans or animals to protect against "B. mallei" infection. "B. mallei" is able to infect humans, so is classed as a zoonotic agent. "B. mallei" was intentionally used to infect animals and humans during World War I. Most organisms within the Burkholderiaceae live in soil; however, "B. mallei" does not. When grown in culture, "B. mallei" grows in smooth, grey, translucent colonies.