细菌是一种极小的,肉眼看不见的,单细胞的植物性微生物。它的种类很多,有的与人类有益不能使人致病,如发酵用的酵母菌、利能使动植物腐收的腐败菌等,我们把它叫做非病原菌。有的封于人类有害能使人致病,这类细菌我们把它叫做病原菌。如伤寒杆菌、霍乱弧菌等就是这一类。我们庄这里所谈的除了普通的病原菌以外,还包括一些比细菌更小或较大的植物性微生物在内。现在分别的写在下面: Bacteria are tiny, invisible, single-celled plant microbes. It’s a lot of types, and some beneficial to human beings can not make people sick, such as yeast for fermentation, Lee can spoil the spoilage of animals and plants, etc., we call it non-pathogenic bacteria. Some of the closures in human harmful can cause disease, such bacteria we call it pathogenic bacteria. Such as Salmonella typhi, Vibrio cholerae and so is this category. What we are talking about here includes, in addition to the common pathogenic bacteria, some plant-based microorganisms that are smaller or larger than bacteria. Now separately written below: