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1. Compare and contrast Archaea and Bacteria.
Archaea differ from Bacteria in the composition of their cell wall and plasma membrane as well as other
features.
The Archaea also possess characteristics in common with domain Eukarya, such as the presence of
histone proteins
in their DNA. No pathogenic Archaea have been described. Most prokaryotes have been placed in
domain Bacteria.
This domain consists of many beneficial as well as pathogenic species. Bacteria are highly diverse and
live in a variety
of environments from the soil to your intestines. Several well-known groups of bacteria are the
cyanobacteria,
proteobacteria,
spirochaetes, chlamydias, and the Gram-positive bacteria.
2 What are three diseases caused by bacteria?
Three diseases caused by bacteria include strep throat, salmonella, and MRSA.
3 What are three helpful bacteria?
Three helpful bacteria include Lactobacillus in yogurt, some Escherichia coli in digesting food, and
Rhizobium in
fixing
atmospheric nitrogen.
4 Describe the major shapes of bacteria, and give an example of each.
The cell shapes of bacteria and their arrangement are used in identification. Rod-shaped bacteria are
known as the
bacilli (singular, bacillus). Examples of bacilli are E. coli, Bacillus anthracis, and Yersinia pestis. The
spherical bacteria
are called the cocci (singular, coccus). The cocci can be highly variable in arrangement. Examples
include Chlamydiae
trachomatis (singular cocci) and Neisseria meningitidis (diplocci). Lactobacillus spp. and Streptococcus
pyogenes
occur in chains called streptocci, and Staphylococcus aureus occurs in chains termed staphylocci.
5 What is the purpose of Gram staining?
In Gram staining, the specimen is treated with a primary stain called crystal violet, followed by iodine as a
fixative,
or mordant. After iodine treatment, the specimen is flushed with alcohol to dehydrate peptidoglycans and
trap the
stain. Next, the specimen is treated with a second stain such as safranin or fuchsin (a pink stain).
Primarily, bacteria
can be divided into Gram-positive and Gram-negative based upon the distinct variations in color as a
result of
differences
in the cell wall. Gram-positive bacteria appear purple after staining. Gram-negative bacteria appear pink.
6 What is the function of the following: cell wall, plasma membrane, plasmid, nucleoid, and pili?
Cell wall—in eubacteria, a peptidoglycan envelope that provides protection and shape
Plasma membrane—a phospholipid bilayer that provides support and regulates the movement of
substances into
and out of the cell
Plasmids—small circular fragments of DNA
Nucleoid—region that houses the bacterial DNA in a single chromosome
Pili—rigid, hairlike structures important for attachment and the exchange of genetic information
7 What are some safety factors to consider when working with bacteria?
x Wear a lab coat or lab apron over your clothes. Use eye protection if required.
x Thoroughly wipe your laboratory table with the provided disinfectant before and after use.
x Thoroughly wash your hands prior to following a procedure and at its completion.
x Always place disposable supplies in the proper container identified by your instructor. Never leave them
lying
around.
x Properly flame all qualified laboratory tools as indicated by your instructor.
x Don’t hesitate to ask questions regarding safety matters.
x Report all potentially hazardous conditions, including spills and potential contamination, to your
instructor.
x Don’t bring any food or drink into the laboratory. Store your book bags, coats, and other personal items
in the
designated area.
x Understand the pathogenic potential of the organisms you are working with in the lab.
8 What causes bioluminescence? How does bioluminescence aid bacteria?
Bioluminescence is the emission of cold light by living things such as fireflies and some jellyfish.
Organisms can
use the light produced by the microbes either as a means of camouflage, as an aid in hunting, or even as
a way
of attracting mates. Bacteria use bioluminescence to be captured by fish. However, the bacteria cannot
be digested
and persist in the gut of the fish. Some scientists claim bioluminescence is vestigial.
9 Why are many scientists alarmed by the overuse of antibiotics? Provide an example of bacterial
resistance along with
its dangerous impact on health and medicine.
The use and overuse of antibiotics has created strains of bacteria resistant to contemporary antibiotics. A
good
example of bacteria that has developed resistance to once-effective antibiotics is methicillin-resistant
Staphylococcus
aureus (MRSA). This highly resistant bacteria is running rampant in hospitals and other public facilities.