Bacteria

A teacher tells her students that bacteria are both helpful and harmful to other organisms and the environment. Which statement could a student give in support of the teacher’s statement?

• Bacteria can survive both in the presence and in the absence of oxygen.

• Bacteria help make a variety of food items and also infect and damage many crops.

• Bacteria can be found in extreme environments like hot springs and the Arctic.

• Bacteria help in the digestion of food and also cause the decomposition of dead organisms.

A student makes a claim that certain bacteria are always harmful to humans. Which example can the student use to support this claim?

• Staphylococcus epidermidis lives on the skin and only causes illness if it enters the body during surgery.

• Escherichia coli fights harmful bacteria in the intestines and causes infections if found in the bladder.

• Streptococcus pyogenes destroys red blood cells and causes illness when it enters the body.

• Clostridium difficile lives in the intestines and only causes illness if it infects a wound.

Most species of E. coli are harmless or even helpful forms of bacteria that are found in the human intestine. E. coli can aid humans in digestion and provide protection from other invading bacteria, but if the bacteria move to the human excretory system, they can replace other naturally occurring bacteria (Lactobaccilli). This can lead to bladder and kidney infections. Researchers found that by replenishing the excretory system with the naturally occurring bacteria, the infection caused by E. coli is cured.

Based on the research, what inference can researchers claim about the effect of bacteria?

• E. coli can only be harmful to humans.

• E. coli is always harmful, and Lactobacilli are always helpful to humans.

• E. coli can be both helpful and harmful to humans.

• E. coli is always helpful, and Lactobacilli are always harmful to humans.

Clostridium difficile is a strain of bacteria that infects the bowel and causes diarrhea. A second bacteria,Lactobacillus casei, is given to patients with diarrhea to slow the growth of Clostridium difficile so the body can rid itself of the remainder of the bacteria. Based on the information, a student claims that all bacteria are not harmful.

Is the claim correct?

• Yes. Lactobacillus casei works with the body to fight off infectious bacteria.

• Yes. Lactobacillus casei can survive in the intestine.

• No. Clostridium difficile causes infections in the bowel.

• No. Clostridium difficile grows too quickly for the body to fight off the bacteria.

Ted observed bacteria under a microscope. He recorded that the bacteria were long and had a beaded appearance.

Which shape of bacteria did Ted observe?

• Bacillus

• Coccus

• Filamentous

• Spirillus

How should Cells 1 and 2 be classified, and why?

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• 
• 
• 

Which student classified the bacteria accurately?

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A student claims that bacteria are beneficial to the soil. The student lists several examples of different purposes of soil bacteria.

Which examples support the claim?

• 1, 2, and 3

• 1, 2, and 4

• 1, 3, and 4

• 2, 3, and 4

A student viewed four different slides of bacteria using a microscope and made a sketch of each one.

How many different bacterial cell shapes were observed?

• 1

• 2

• 3

• 4

A student made a table to list features of some organisms when viewed under a microscope.

Which organism can be categorized as a bacillus bacterium?

• 1

• 2

• 3

• 4