Exam 10: Identifying and Classifying Microorganisms

You have isolated a bacterium from a contaminated river but you are unable to culture it in the laboratory. Which method could you use to identify the organism?

A DNA similarity of 75% between two organisms

Based on DNA hybridization, humans and chimpanzees are the same species.

Size and shape may allow one to differentiate between a bacterium, fungus, and protozoan.

When DNA probes are used to identify bacterial DNA similarities by hybridization, the probe DNA is heated and the template DNA is treated to separate the two strands. Why would the probe DNA be heated?

All known species of bacteria are described in Bergey's Manual of Systematic Bacteriology.

If the GC content of two organisms is 45% in both,

In the 1930s Kluyver and van Niel proposed a classification scheme based on

Phage typing

Strain differences are helpful in

DNA probes have been very useful in

Horizontal DNA transfer may make it more difficult to construct phylogenetic trees.

Wisconsin state health authorities alerted the CDC about an E. coli O157:H7 outbreak. Soon thereafter, officials from two other states reported that they also had cases of illness associated with this pathogen. Within days, the CDC determined that the E. coli strains from all three states were the same, and the likely source of the outbreak was a particular brand of pre-packaged fresh spinach. The CDC then issued a press release advising people not to eat bagged fresh spinach. -E. coli is a Gram-negative bacillus that is found as intestinal normal microbiota. Which of the following would not be useful for an initial step in identifying E. coli O157:H7 strains in a stool sample?

Wisconsin state health authorities alerted the CDC about an E. coli O157:H7 outbreak. Soon thereafter, officials from two other states reported that they also had cases of illness associated with this pathogen. Within days, the CDC determined that the E. coli strains from all three states were the same, and the likely source of the outbreak was a particular brand of pre-packaged fresh spinach. The CDC then issued a press release advising people not to eat bagged fresh spinach. -If you were the lab technician trying to identify the causative organism of this foodborne outbreak, would you inoculate several biochemical tests at the same time, or would you inoculate each test after getting the results from the previous test?

From most general to most specific, which is the correct order?

If the GC content of two organisms is 60%, the

Various strains of E. coli

In 1908 Orla-Jensen suggested that bacteria be grouped according to their

In 1970 Stanier proposed that classification be based on

Serratia marcescens are red when incubated at 37°C.