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To all those who purchased Through the Microscope after 5/23/2013. Your textbook is the 5th edition of Through the Microscope. Please navigate to the above link and log in there. If you purchased Through the Microscope before 5/23/2013, you purchased access to the 4th edition and you are on the correct site. The 4th edition will remain accessible until at least December of 2013. At that time it will be retired.
This is the third edition of Through the Microscope. A new edition has just been published. Please go to the Table of contents for the fourth edition
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For obvious reasons we have focused on growing cells, but there are non-growing states of microbes that are important to both microbes and humans. In these states, termed spores and cysts, the cells remain dormant for long periods of time. Part of the relevance of these states is that the very properties that allow the cell to survive extended time periods also happen to make the cells resistant to our typical efforts to kill them. As a consequence, the attempt to sterilize a sample can be thwarted by the presence of bacterial spores or cysts. In this section we examine some of the properties of these structures.
Spores and cysts are resting structures. That is, these states have very low to nonexistent rates of metabolism. They are common in organisms that live in soil and may need to survive some rough conditions such as lack of nutrients, high heat, radiation, or drying.
Sporulation is a unique developmental cycle. After the decision to sporulate is made, creation of a different type of cell needs to take place, which requires turning on a large collection of genes in a tightly coordinated fashion. In addition, all of this expression has to be finished before the microbe runs out of energy. There are several types of spores. Some are highly resistant structures that are formed under conditions of cell stress and are created inside a supportive cell and are termed endospores. Others are part of the normal reproductive cycle, being created by differentiation of a vegetative cell and we will refer to these as spores. In this section we talk generally about the structure of spores and in the chapter on Regulation we will examine the regulation of sporulation.[Prev] | [Next]