Spirochaeta

例句：

1. 1. The bacteria that cause stomach ulcers are called spirochaetes.
   导致胃溃疡的细菌被称为螺旋体。
2. 2.The study of these microorganisms is important for understanding the human body's immune system.
   研究这些微生物对于理解人体的免疫系统非常重要。
3. 3. The spirochaetes were discovered in the 19th century by a French scientist.
   螺旋体是在19世纪由一位法国科学家发现的。