Bio 205 chapter 5

At what phase does broth become turbid and visible colonies appear on agar in the bacterial growth curve?

Log phase

At what point in the bacterial growth curve are bacteria the most vulnerable to antibiotics?

Log phase

At what stage of the bacterial growth curve are the bacteria dividing rapidly and the graph is rising in a straight line?

Log phase

In humans, at what stage of the bacterial growth curve are disease symptoms developing because the bacteria are causing tissue damage?

Log phase

Most of the human pathogens are

Mesophiles

You have isolated an organism from the human intestinal tract. It grows better when you capped the culture tube with a semipros plug than when you used a plug that is completely permeable to oxygen. This organisms should be classified as a

Microaerophile

Which of the following is not a limiting factor for the growth of microorganisms?

Not enough humidity

Which of the following types of media are examples of a chemically undefined medium, or complex medium?

Nutrient agar

The stomach protects us from a large number of microbes that might be in our because

Of its high level of acidity

As a culture of Clostridium enters the decline phase of the growth curve, the vegetative cells will have

Produced endospores

An organism that grows at 5 C is classified as a

Psychrophile

A mesophilic bacterium could

Reproduce at 37 C Produce human disease Grow at human body temperature

A soil sample is added to a culture medium that has been deigned to promote the growth of the genus Pseudomonas while inhibiting the growth of fungi. The test uses a

Selective medium

The agar in nutrient agar serves as a

Solidifying agent

Which of the following methods of measuring population growth is a direct count?

Standard plate count using a dilution series

There are some mesophilic bacteria that are salt tolerant. An example is

Staphylococcus

At what phase in the bacterial growth curve in a patient do antibodies from the immune system and phagocytosis by white blood cells affect the process of the disease?

Stationary phase

At what stage of the bacterial growth curve do the reproductive and death rates equalize?

Stationary phase

In a culture tube at what phase of the bacterial growth curve do available nutrients become scarce and waste products begin to accumulate?

Stationary phase

Which one of the following diseases does not involve endospores?

Syphilis

Which of the following conditions are most likely to affect the growth of bacteria?

Temperature, oxygen and pH

When relating generation time of microbes to disease, which is a correct general statement that could be made?

The faster the generation time, the shorter the incubation period

How does the GasPak system work?

The hydrogen in the GasPak reacts with oxygen in the presence of a catalysts to form water, thereby creating an oxygen-free atmosphere

In the log phase of growth

The number of cells in the population increase rapidly

How can you take a mixed unknown sample and separate out pure colonies to identify them?

The pour plate method of mixing the sample with melted agar, then poured into petri dishes and allowed to harden A sterila loop can take a sample and streak for solution onto an agar plate An individual colony can be subcultured onto another agar plate

Hyperthermophile

These have been found in seawater rom hot water volcanic events

Thermophile

These organisms are present in compost piles and hot springs

Barophile

They are able to withstand high pressure

Aerololerant

They are insensitive to oxygen and still grow well when oxygen is present

Acidophile

They can tolerate acidic pH 2.0 to a pH 9.5

Anaerobe

They do not or cannot use oxygen

Facultative anaerobe

They grow in either the presence of or a reduced concentration of oxygen

Psychrotroph

They organisms live at the bottom of the ocean

Capnophile

They require an atmosphere low in oxygen but rich in carbon dioxide

Halophile

They require relatively high levels of salt

Microaerophile

They survive in environments where the concentration of oxygen is relatively low

Mesophile

This group has most of the pathogens as they grow at body temperature

Obligate anaerobe

This group requires oxygen for metabolism, just like us

Which of the following statements about generation time is correct?

Under optimal conditions some prokaryotes have a very fast generation time of 20-30 minutes Some organisms have much slower generation times of 20-30 hours

An acidophils would grow best at a pH of

2

Under what conditions would you find vegetative growth from Clostridium botulinum endospores?

A vacuumed seal can of food

____ are important food producing bacteria because they can be used to produce dairy products like buttermilk, sour cream and yogurt from milk and cream.

Acidophiles

A selective medium is one that

Allows one type of bacterium to grow while inhibiting another type

How is asexual reproduction used in prokaryotic cells?

An increase in the population size with each cell being identical to the parent cell

How does cytokinesis work in prokaryotes?

An inward pinching of the cell envelop, tubular homolog is part of the fission ring

A bacterium that grows only at the bottom of a thioglycollate broth tube should be classified as

Anaerobic

Bacteria that can grow only in the absence of oxygen are said to be

Anaerobic

Psychrophiles and thermophiles differ with respect to their

Best temperature for growth

Archaea reproduce by a process known as

Binary fission

The process by which bacteria reproduce is known as

Binary fission

Which of the following diseases are all caused by endospore forming Clostridia?

Botulism Gas gangrene Tetanus

An example of a mesophile that is most frequently identified cause of infective diarrhea is

Campylobacter

Some organisms like Neisseria grow well in an atmosphere that is low in oxygen and rich in carbon dioxide. What is the best name for these organisms?

Capnophiles

In a bacterial growth curve, when the number of dying cells exceeds the number of new cells formed, what stage are they in?

Decline phase

Endospores are heat-stable resting forms of all of the bacteria listed below except

Escherichia coli

A bacterium that grows turbid throughout a thioglycollate broth tube should be classified as

Facultative

The interval time between successive binary fission of a cell or population of cells is known as the

Generation time

Endospores are found primarily in which kind of organism?

Gram-positive bacillus

Facultative bacteria are those that

Grow in the presence or absence of oxygen

What are organisms called that require high amounts of salts?

Halophiles

Endospores are very difficult to destroy. Because of this, which of the following techniques will work to get rid of them?

Heat them under high pressure for several hours

Under the conditions of bioterrorism where were endospores from Bacillus anthraces found?

Inside an envelop On the surface of the skin On the surface of machinery like in the mail sorting room

An important contribution was made to microbiology with the introduction of agar by Robert Koch. Which of the following statements about agar is correct?

It contains no essential nutrients It remains liquid until cooled below 36 C As a solid in a petri dish it is useful to isolate pure colonies

At what stage in the bacterial growth curve are the bacteria growing in size, storing nutrients, and synthesizing enzymes in preparation for binary fission?

Lag phase

At what stage in the bacterial growth curve are there no cell divisions occurring, because the bacteria are adapting to their new environment?

Lag phase

Which of the following is not one of the four phases of a bacterial growth curve?

Lead phase

A bacterium that grows only at the top of a thioglycollate broth tube should be classified as

aerobic

Most bacteria grow best as

neutral pH