8-2 Enrich: Identifying Bacteria

Name ____________________________________ Date __________ Class ___________________
SECTION 8-2
ENRICH
Identifying Bacteria
About 5,000 different kinds of bacteria inhabit Earth. Each kind can be distinguished from the others by its characteristics. In addition to shape, these characteristics include: whether it will grow in water hotter than 45ºC; whether it will
grow in very salty water; whether it will grow in the presence of air, whether it
will grow without air; and whether it forms endospores.
Scientists who study viruses use these and about 15 other characteristics to
identify a bacterium. The chart below shows some of the characteristics of six
common bacteria. A plus (!) sign means the bacterium has the characteristic.
A minus (") sign means the bacterium does not have the characteristic.
Bacterium
Rod
Sphere
Grows
at 45ºC
Grows in 6.5%
Salt Water
Grows
in Air
Grows
Without Air
Endospores
1
!
"
!
unknown
!
!
!
2
!
"
!
unknown
"
!
!
3
"
!
"
!
!
!
"
4
!
"
!
"
"
!
"
5
"
!
"
"
!
!
"
6
"
!
!
"
!
!
"
Answer the following questions on a separate sheet of paper.
1. What characteristic do all of the bacteria have in common?
2. How could you distinguish bacterium 1 from bacterium 2?
4. What characteristic(s) can you use to distinguish the sphere-shaped bacteria
from one another?
5. Sea water is about 3.5% salt. In some places, sea water gets trapped when the
tide goes out. The heat of the sun will cause some of this water to evaporate.
Which bacteria are most likely to survive in such water? Explain your answer.
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U nit 3 Reso urces
Scie nce Explorer Focus o n Lif e Scie nce
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3. Which bacteria might be found in hot springs?