Chapter 26
Environmental Microbiology
Chapter Summary and Essay Questions
This chapter discusses water microbiology and elemental recycling in the environment. Chapter
26 opens with discussions on the microbial floras of unpolluted, polluted, and marine
environments. It then outlines infectious diseases that water can transmit and continues with
descriptions of water purification and sewage treatment. The laboratory bacteriologist is
highlighted, and the chapter closes with descriptions of the roles of microorganisms in the carbon,
sulfur, and nitrogen cycles. On completing the chapter, you should be able to answer the
following questions:
a. Compare ground and surface waters with reference to their origin and microbial content.
b. Write short essays on unpolluted, polluted, and marine environments, comparing the types
of microorganisms found in each environment.
c. Discuss the origin of physical, chemical, and biological pollution of waters.
d. Explain the meaning of BOD, and outline the test by which it is determined.
e. List a number of bacterial, viral, and protozoal diseases that can be transmitted by
contaminated waters.
f. Describe the three major steps involved in the purification of waters by major municipalities.
g. Compare the basis for sewage disposal in the cesspool and the septic tank.
h. Outline the process involved in the treatment of commercial sewage during the primary,
secondary, and tertiary stages.
i. Assess the importance of biofilms in a watery environment.
j. List the major steps involved in the performance of the standard plate count technique and
the most probable number test as they are used in water bacteriology.
k. Assess the role of microorganisms in the earth’s carbon cycle.
l. Briefly describe the sulfur cycle as it occurs in the soil.
m. Assess the importance of soil microorganisms to the nitrogen cycle, indicating where
microorganisms are important and highlighting their role in the process of nitrogen fixation.