Many Dangerous Microbes Co-Opt their Host’s Own Molecular Structures.

Reading passage question

Many dangerous microbes co-opt their host’s own molecular structures. For example, Shigella flexneri is a rod-shaped bacterium that causes severe intestinal discomfort in humans. Shigella contains a gene called IcsA that allows it to appropriate actin filaments inside the host’s infected cell. Actin is normally used to provide structure and form to the cell, but the microbe forms the fibers into a propulsive tail that moves it freely from cell to cell. To appropriate the actin, Shigella sticks to the epithelial cells of the intestinal lining. Once there,it signals the epithelial cell to alter its own shape and pulls the microbe inside. Once Shigella is ensconced within the cytoplasm, it begins replicating. The replicants can then make use of the IcsA gene and create their own tails from the cell’s actin, spreading the infection to other cells. Thus, the bacterium bypasses the blood and lymph systems entirely, which allows it to avoid alerting the body’s immune system.

Researchers tested the IcsA hypothesis by transferring the gene into E. coli bacteria and then placing the bacteria inside host cells. The organisms formed actin tails and began behaving much as the Shigella bacteria did. Such microbes as Listeria monocytogenes also co-opt host actin, though a different gene is involved in the process.

“Many dangerous microbes co-opt their host’s own molecular structures.”- is a GMAT reading comprehension passage with answers. Candidates need a strong knowledge of English GMAT reading comprehension.

This GMAT Reading Comprehension consists of 7 comprehension questions. The GMAT Reading Comprehension questions are designed for the purpose of testing candidates’ abilities in understanding, analysing, and applying information or concepts. Candidates can actively prepare with the help of GMAT Reading Comprehension Practice Questions.

Questions and Solutions

1. It can be inferred from the passage that which of the following is true of the blood and lymph systems?

1. The blood and lymph systems are in some way linked to the immune system.
2. The blood and lymph systems are not able to overcome most bacterial infections.
3. The blood and lymph systems are used by IcsA genes to obtain actin for the creation of propulsion tails.
4. The blood and lymph systems signal noninfected epithelial cells to deny actin filaments to intrusive microbes.
5. The blood and lymph systems will be alerted to the presence of a Shigella flexneri infection when a microbe infects a white blood cell.

2. According to the author, what happens after a Shigella flexneri microbe enters a host cell?

1. The microbe depletes the nutrients in the cytoplasm and creates a replica of the original cell.
2. The microbe duplicates itself, and the duplicates form actin tails and spread to other cells.
3. After using the IcsA gene to signal to the invaded cell, the microbe spreads through the cellular lining.
4. By avoiding the immune system, the microbe spreads quickly through the blood stream.
5. The microbe first develops a propulsive tail out of actin, then co-opts the host's molecular form.

3. According to the passage, the IcsA gene is believed to control the development of actin tails for which of the following reasons?

1. The formation of actin tails cannot be attributed to any other cellular structure associated with Shigella flexneri.
2. Experiments have shown that when IcsA genes are transferred into E. coli, they develop actin tails.
3. Shigella flexneri without the IcsA gene do not grow tails formed from actin filaments.

1. I only
2. II only
3. I and II only
4. I and III only
5. II and III only

4. According to the passage, which of the following best describes one function served by actin?

1. Regulating the speed at which bacterial infections move through the body
2. Supplying the material needed to provide the shape of a typical cell
3. Releasing specific chemical agents which counteract foreign microbes
4. Interacting with the cytoplasm to aid the replication of epithelial cells
5. Providing necessary genes for invading Shigella flexneri bacterium

5. According to the passage, the Shigella flexneri bacterium is a dangerous microbe because it

1. has a unique shape that allows it to control cells in the intestinal lining
2. forms its actin tails by depleting necessary actin from infected cytoplasm
3. manipulates the IcsA gene within the epithelial cells
4. is not involved in the genetic co-opting of the cell
5. exploits existing cell structures to spread undetected by the body's defenses

6. According to the passage, Shigela flexneri invades epithelial cells by

1. attacking the actin reservoirs within host intestinal cells, thereby affecting epithelial genes
2. replicating corollary cells within the human blood and lymph system
3. attaching itself to epithelial cells and gradually consuming the outer membrane of the cells
4. entering epithelial cells by prompting them to modify their existing form
5. weakening the epithelial lining and opening the body for further infection

7. Which of the following is an assumption made by the researchers mentioned in highlighted text?

1. E. coli do not typically spread among cells by forming tails out of actin filaments.
2. The IcsA gene of Shigeila faxneri will not directly affect a host cell.
3. The listeria monocytogenes microbe operates in a manner analogous to the Shigella faxneri bacterium.
4. Epithelial cells react in a consistent way when removed from a human body.
5. The formation of a propulsive tail from nreeyistina cell matter is an uncommon method of microbial dissemination.

Suggested GMAT Reading Comprehension Samples

• The System of Patent-Granting, Which Confers Temporary Monopolies for the Exploitation of New Technologies
• Traditional Social Science Models of Class Groups in the United States are Based on Economic Status
• Solar Ponds are Bodies of Water in Which Circulation is Incomplete and There is a Very High Salt Concentration that Increases with Depth
• Ethnohistoric Documents from Sixteenth-Century Mexico Suggesting that Weaving and Cooking were the Most Common Productive Activities for Aztec Women
• A Recent Study has Provided Clues to Predator-Prey Dynamics in the Late Pleistocene Era.
• Although the Industrial Union Organizations that Emerged Under the Banner of the Congress of Industrial Organizations
• According to P. F. Drucker, The Management Philosophy Known as Total Quality Management
• The Professionalization of the Study of History in the Second Half of the Nineteenth Century
• Conventional Wisdom has it that Large Deficits in the United States Budget Cause Interest Rates to Rise.
• In a New Book About the Antiparty Feeling of the Early Political Leaders of the United States
• Citing the Fact that the Real Gross Domestic Product (GDP) per capita was Higher in 1997
• The General Density Dependence Model can be Applied to Explain the Founding of Specialist Firms
• In the 1980's, Astronomer Bohdan Paczynski Proposed a Way of Determining Whether the Enormous Dark Halo Constituting the Outermost Part of the Milky Way Galaxy
• The United States Hospital Industry is an Unusual Market in that Nonprofit and For-Profit Producers Exist Simultaneously.
• The Black Death, a Severe Epidemic that Ravaged Fourteenth Century Europe
• The United States Government has a Long-Standing Policy of Using Federal Funds to Keep Small Business Viable.
• Comparable Worth, as a Standard Applied to Eliminate Inequities in Pay
• Some Historians Contend that Conditions in the United States During the Second World War
• More Selective than Most Chemical Pesticides in that they Ordinarily Destroy only Unwanted Species
• Historians have Identified Two Dominant Currents in the Russian Women's Movement of the Late Tsarist Period.