Bio. Ch 4: Dynamic of Microbial Growth

The enzyme superoxide dismutase converts superoxide into ______. O2 and H2 H2 and H2O H2 and H2O2 O2 and H2O2 O2 and H2O

O2 and H2O2

Which of the following are true statements regarding reactive oxygen species (ROS)? ROS are formed as byproducts of aerobic respiration. ROS are used by obligate anaerobes instead of O2. ROS are commonly found in anaerobic environments. ROS are toxic to obligate anaerobes, which typically lack protective mechanisms. ROS can damage cell components.

ROS are formed as byproducts of aerobic respiration. ROS are toxic to obligate anaerobes, which typically lack protective mechanisms. ROS can damage cell components.

Why is prompt refrigeration of leftover food an effective way to prevent food spoilage? Refrigeration destroys most microbes that lead to food spoilage and food-borne illness. Refrigeration temperatures are not optimal for reproduction and growth of food-associated pathogens. Refrigeration denatures most toxins that may have been produced by food-associated microbes.

Refrigeration temperatures are not optimal for reproduction and growth of food-associated pathogens.

Which of the following contain nitrogen? RNA fats DNA proteins carbohydrates

RNA DNA Proteins

Many bacterial communities secrete polysaccharides and other hydrophilic polymers. This mesh-like accumulation can help protect the bacteria growing within from antibiotics or disinfectants. These communities are called _____

biofilms

Which of the following are required for proper isolation of microorganisms? nutrient broth in a tube inoculation tools an agar plate a syringe

inoculation tools an agar plate

A liquid or solid substance that supports the growth and multiplication of microorganisms is called a culture _____

medium

Which of the following does not describe interactions of mixed microbial communities? Some microbes can synthesize toxic compounds to inhibit competitors. Microbes can interact cooperatively and even foster the growth of species that otherwise could not survive. Conditions in mixed microbial associations are readily reproduced in the laboratory. Microbes can compete for nutrients. Microbial cells can consume O2, creating microenvironments in which anaerobes can thrive.

Conditions in mixed microbial associations are readily reproduced in the laboratory.

_____ phase describes the initial phase after bacterial cells are placed into a new environment and are gearing up for cell division, but their numbers have not yet increased.

Lag

Bacteria and archaea typically divide by a process known as _____ _____

binary fission

What term is used to describe a group of microbes co-existing in polymer-encased communities? biofilm biolayer slime film slime layer

biofilm

Hydrogen peroxide is broken down into water and O2 by the action of the enzyme _____

catalase

Which enzyme converts hydrogen peroxide, formed in aerobic respiration, to water and O2? catalase hydrogenase dismutase dehydrogenase

catalase

If the solute concentration is higher outside the cell than inside the cell, water will diffuse out due to osmosis. This will result in _____

plasmolysis

Match the term on the left with the description of the optimum temperature environment. Instructions psychrophile psychrotroph mesophile thermophile

psychrophiles - cold arctic regions mesophile - human body thermophile - compost heap psychrotophs - refrigeration

A _____ culture contains only ONE species of microorganisms descended from a single cell.

pure

The _____ phase of the bacterial growth curve is when there are an equal number of cells dividing as there are dying.

stationary

During which phase of growth does the number of new cells balance the number of declining cells? lag phase death phase stationary phase log phase

stationary phase

A _____ medium means that the medium does not contain any viable microbes.

sterile

The _____ - _____ method involves the use of a sterile loop in order to isolate a pure culture of bacteria onto an agar plate.

streak - plate

Consider the following environmental factors. Which have the most impact on microbial growth? wind speed pH odor temperature oxygen availability water availability

temperature pH water availability oxygen availability

Assuming you begin with a single bacterial cell that has a doubling time of 15 minutes, how many cells would you find at the end of one hour?

16

If you start with a single bacterial cell that has a generation time of 20 minutes, there will be _____ cells after one hour.

8

Which of the following describe or relate to a Petri dish? It is an airtight container that maintains culture purity. A culture medium in a Petri dish can be referred to as a plate of that medium, e.g., an agar plate. It is a two-part covered container made of plastic or glass. It excludes airborne contaminants.

A culture medium in a Petri dish can be referred to as a plate of that medium, e.g., an agar plate. It is a two-part covered container made of plastic or glass. It excludes airborne contaminants.

Which of the following is most likely to be a pure culture? A Petri dish covered with bacteria following inoculation from a single patient. A bacterial lawn of growth covering an agar plate. A broth culture growing in a flask. A single colony growing on a streak plate.

A single colony growing on a streak plate.

For many hundreds of years, people have often preserved food by which of the following methods? - Adding large amounts of salt or sugar - Sealing them raw in airtight containers - Refrigerating them to inhibit microbial growth - Keeping the foods hydrated so they would not dry out

Adding large amounts of salt or sugar

A sterile medium is characterized by which of the following? an absence of nutrients lack of growing microbes an absence of viable microbes

An absence of viable microbes

From which body site could a facultative anaerobe be isolated? surface of skin any of these locations intestine deep wound

Any of these locations

Which of the following descriptions of biofilms are true? - Biofilms are involved in a small percentage of bacterial infections. - Bacteria in biofilms can be hundreds of times more resistant to disinfectants than their free-living counterparts. - Biofilms are able to enhance many bioremediation efforts. - Biofilms are involved in dental plaque, which can lead to tooth decay and gum disease. - Biofilms are important in wastewater treatment facilities.

Biofilms are able to enhance many bioremediation efforts. Biofilms are involved in dental plaque, which can lead to tooth decay and gum disease. Biofilms are important in wastewater treatment facilities. Bacteria in biofilms can be hundreds of times more resistant to disinfectants than their free-living counterparts.

Which of the following characterizes the lag phase of a normal bacterial growth curve? - Cells are synthesizing enzymes needed for growth but not increasing in number. - Cells are undergoing logarithmic cell division. - Depletion of nutrients and buildup of waste. While some cells multiply, others die, and the overall population remains relatively constant. - Cells are declining exponentially.

Cells are synthesizing enzymes needed for growth but not increasing in number.

Which microorganism uses inorganic chemicals for energy and carbon dioxide for carbon? Chemolithoautotroph Photoautotroph Heterotroph

Chemolithoautotroph

Prokaryotes that derive their energy from sunlight and carbon from organic compounds are called which of the following? Phototrophs Photoheterotrophs Photoautotrophs Chemoheterotrophs

Photoheterotrophs

Place the steps in biofilm formation in the correct order. Start with the earliest at the top.

Planktonic bacteria move to the surface and adhere bacteria multiply and produce extracellular polymeric substances (EPS) Other bacteria may attach to the EPS and grow Cells communicate and create channels in the EPS that allow nutrients and waste product to pass Some cells detach and then move to other surfaces to create additional biofilms

Which environment is more dynamic and complex? A laboratory environment Soil and its surroundings

Soil and its surroundings

Since stationary phase is marked by the drop in concentration of provided nutrients following log phase growth, how is it that some cells can continue to multiply? Some cells are unaffected by the lack of nutrients and buildup of waste. Stationary phase is short enough that some cells are able to continue growing despite the lack of nutrients. Some cells continue to live off the secondary metabolites they synthesized during late log phase. Some cells die off, often bursting and releasing nutrients that are then available for other cells.

Some cells die off, often bursting and releasing nutrients that are then available for other cells.

True or false: A colony is a distinct mass of microorganisms which develop from a single cell growing on a solid medium.

True

If O2 is present in an environment, it is said to be _______. aerotactic aerobic aerophilic

aerobic

Nitrogen fixation is the process by which some prokaryotes convert atmospheric nitrogen into _____ and then incorporating that into cellular material.

ammonia / NH3

An environment with little or no O2 present is called a(n) _____ environment

anaerobic

In which phase of the growth curve is the generation time measured? lag log death stationary

log

A flat covered container made from plastic or glass in which a solid culture medium can be added is called a _____ _____

petri dish

An autotrophic organism that uses light for energy and carbon dioxide as a carbon source is termed a

photoautotroph

True or false: Obligate anaerobes cannot multiply if O2 is present and are often killed by exposure to air because they typically lack the enzymes to degrade reactive oxygen species.

true

The following are steps involved in obtaining a pure culture using the streak-plate method. Place them in the correct order starting from the top.

- a sterile inoculating loop is dipped into microbe-containing sample - the inoculating loop is drawn several times across the surface of a sterile agar plate - the loop is sterilized and a new series of parallel streaks is made across and at an angle to the original ones - the loop is sterilized and a final set of parallel streaks is made, dragging into the area some organisms from the previous section - the petri dish is incubated; distinct, well isolated colonies form from cells that were separated sufficiently

Microorganisms with an optimum temperature between 45οC and 70οC, commonly found in hot springs and compost heaps, are called

thermophiles

Choose the correct properties of agar that make it such a good agent to solidify culture media when compared with other options. - Agar is not destroyed by high temperatures and so can be sterilized by heating. - Melted agar stays liquid until cooled below 45 degrees C. - Solidified agar remains solid until heated above 95 degrees C. - Agar serves as a good nutrient source for many microbes, allowing good growth on the media. - Very few microbes can degrade agar.

-Agar is not destroyed by high temperatures and so can be sterilized by heating. - Melted agar stays liquid until cooled below 45 degrees C. - Solidified agar remains solid until heated above 95 degrees C. -Very few microbes can degrade agar.

True or false: Agar, which is used to solidify culture media, provides a rich nutrient source that supports the growth of colonies of bacteria.

False

Which of the following are true regarding freezing? Freezing prevents all microbial growth. Freezing is a common method used to preserve stock cultures of bacteria. Freezing is a good method for preserving foods for long-term storage. Freezing is an effective means of destroying microbes.

Freezing is a common method used to preserve stock cultures of bacteria. Freezing is a good method for preserving foods for long-term storage.

You would be most likely to find thermophiles in which of the following locations? hot springs as part of the human microbiota compost heaps inside air conditioned buildings in the soil in front of your home

Hot springs Compost Heaps

Where are you most likely to find biofilms?

In dental plaque on teeth In toilet bowls and sink drains On rocks in a stream bed In pipes, drains, and water towers In the majority of bacterial infections

Choose the best description(s) of bacteria found during stationary phase of the growth curve. Some cells utilize nutrients released by other dead cells in order to multiply. The total number of viable cells remains relatively constant. Some cells in the population are dying while others are dividing. Secondary metabolites are not produced during stationary phase. The length of time cells spend in stationary phase is constant within a species, regardless of environmental conditions.

Some cells utilize nutrients released by other dead cells in order to multiply. The total number of viable cells remains relatively constant. Some cells in the population are dying while others are dividing.

The method of using a sterile loop to spread a small culture sample over a medium in a pattern that gradually thins out the sample, resulting in isolated colonies, is called which of the following? inoculation plate method spread plate method loop dilution/ pour plate method steak plate method

Streak plate method

The causative agent of strep throat, _______ is an example of an obligate fermenter. Staphylococcus aureus Streptococcus pyogenes Streptomyces griseus

Streptococcus pyogenes

Which answer best explains the events in the figure leading to plasmolysis? - There is more solvent outside the cell than inside, so water exits the cell. - The solute concentration of the medium is greater than that in the cell, causing water to diffuse out of the cell due to osmosis. - The solute concentration inside the cell is greater than outside the cell, causing water to diffuse out of the cell via osmosis. - There is a greater concentration of water outside the cell, so water flows from inside to outside the cell.

The solute concentration of the medium is greater than that in the cell, causing water to diffuse out of the cell due to osmosis.

Which of the following describe aseptic techniques used in the laboratory? They are used to keep containers, media, and instruments sterile prior to use. They include antimicrobial substances applied to living tissue and skin. They are important to minimize the chance of contaminating pure cultures.

They are used to keep containers, media, and instruments sterile prior to use. They are important to minimize the chance of contaminating pure cultures.

Which of the following correctly describe facultative anaerobes? They can grow in the presence of O2 but do not use it to harvest energy. They can only grow in the absence of O2. They can grow without O2. Their growth is faster when O2 is available.

They can grow without O2. Their growth is faster when O2 is available.

How do high levels of salt or sugar (for example, salt in bacon or anchovies or sugar in jams, jellies, and honey) work to preserve food? They reduce water availability, making it difficult for food spoilage microbes to grow. They create a hypotonic environment that leads to plasmolysis of bacterial cells. They encourage growth of beneficial microbes, which outcompete food spoilage microbes.

They reduce water availability, making it difficult for food spoilage microbes to grow.

True or false: As a result of exponential multiplication, a few cells of a pathogen may give rise to thousands in only a matter of hours.

True

An _____ requires only carbon dioxide as a sole carbon source.

autotrophs

Tetanus and gangrene are deep tissue infections associated with tissue damage that limits circulation. With which type of bacteria would you expect these to be associated? microaerophilic anaerobic aerobic

anaerobic

The five groups used to categorize microorganisms with respect to growth temperature (psychrophile, psychrotroph, mesophile, thermophile, and hyperthermophile) ______. represent the entire range at which the organisms in the groups can grow. are based on optimum growth temperatures. are precise with respect to the dividing lines between each group.

are based on optimum growth temperatures.

Procedures that minimize the chance of contaminating a pure culture are called _____ techniques

aspetic

Match up the following groups of prokaryotes according to the energy and carbon sources they use. photoautotroph photoheterotroph chemolithoautotroph chemoorganohetertroph

chemoorganoheterotroph- energy; organic compounds; carbon ; organic compounds photoautotroph - energy; sunlight; carbon; CO2 photoheterotroph - energy; sunlight; carbon; organic compounds chemolithautotroph - enery; inorganic chemicals; carbon ; CO2

Which term describes organisms which acquire their energy from chemical compounds? chemotrophs phototrophs autotrophs

chemotrophs

An isolated _____ is a distinct mass of microorganisms appearing on a solid medium, arising from the multiplication of a single cell.

colony

What type of disease or injury would you expect to be most closely associated with obligate anaerobic pathogens? Pneumonia or lung disease Deep tissue wound Superficial skin injury

deep tissue wound

A limiting nutrient ______. is synthesized by the cell in order to allow growth prevents microbial growth due to its toxicity dictates the maximum level of microbial growth

dictates the maximum level of microbial growth

Consider interactions of mixed microbial communities. Match the descriptions in the left column with those that best correlate with them in the right column.

difficult to reproduce - conditions in close microbial associations simpler to reproduce in the laboratory - pure cultures inhibit competitors - synthesis of toxic compounds nutrients for another microbe - production of metabolic wastes by one microbe creation of low O2 microenvironment - consumption of O2 by aerobic growth

The superoxide (O2-) that is produced during aerobic respiration is harmful. Organisms that grow aerobically can convert peroxide into O2 and H2O2 by the action of the enzyme superoxide

dismutase

Bacteria growing in a natural environment experience ______. dynamic and complex conditions conditions similar to that of the laboratory

dynamic and complex conditions

Mycobacterium leprae, the causative agent of Hansen's disease (leprosy), grows best at temperatures below the usual core human body temperature of 37∘C. Because of this temperature preference, Hansen's disease most commonly involves which regions of the human body? ears heart hands gastroinestinal tract fingers

ears hands fingers

Microorganisms are designated as photoautotrophs or chemoheterotrophs according to the _____ and _____ sources they use

energy carbon

The log (logarithmic) phase of a normal growth curve is also referred to as the _____ phase

exponential

Ten cells of a pathogen may give rise to over 40,000 cells in only a matter of hours as a result of ______. additive cell growth exponential growth

exponential growth

The characteristic slimy appearance of a biofilm is primarily due to polymers secreted by the microbes present in them. These polymers are referred to as _____ _____ _____ (EPS)

extracellular polymeric substances (EPS)

Some microorganisms live in harsh environments that kill most other organisms. The term used to describe an organism with this characteristic is _____

extremophiles

Autotrophs play a crucial role in the cycling of carbon in the environment by converting inorganic carbon to an organic form. This process is called carbon _____

fixation

An organism that must consume organic matter is called a(n) _____

heterotroph

Which type of organism requires organic compounds for its carbon and energy needs? heterotroph autotroph phototroph

heterotroph

An organism that gets its energy directly from sunlight is called a(n) _____

phototrophs

Which term is used to describe organisms that can obtain energy directly from sunlight?

phototrophs

Treponema pallidum, the causative agent of syphilis, grows best in cooler regions of the human body. Because of this, for many years, treatment of syphilis involved ______. placing the patient in an ice bath having the patient lie still in bed inducing fever in the patient

inducing fever in the patient

Which of the following describes the optimum temperature of a psychrophile relative to a thermophile? it is the same as a thermophile it is lower than a thermophile it is higher than a thermophile

it is lower than a thermophile

A normal bacterial growth curve is characterized by five stages. What are they? recovery lag stationary death latency prolonged decline exponential incubation

lag phase exponential or log phase stationary phase death phase phase of prolonged decline

Imagine an environment that contains plenty of carbon, nitrogen, sulfur, and potassium, but very low levels of phosphorus and iron. In this case, phosphorus and iron would be ______. limiting nutrients major elements macromolecules

limiting nutrients

What term is used to describe chemical substances such as carbon or phosphorous, which are found in large quantities in cells? major element macroelement megamolecule macromolecule macrocompound

major element

Carbon, oxygen, hydrogen, nitrogen, sulfur, and phosphorus, are examples of chemical substances called _____ _____, which are the essential components of the cell's macromolecules.

major elements

Which of the following are examples of chemotrophs? photosynthetic bacteria mammalian cells bacterial pathogens of humans fungi algae

mammalian cells fungi bacterial pathogens of humans

In the laboratory, a liquid or solid ______ provides nutrients for microbial growth. agar broth medium

medium

E. coli and most other common bacteria are ___. hyperthermophiles mesophiles thermophiles psychrotrophs psychrophiles

mesophiles

Human pathogens, adapted to growth in the human body, are ______. psychrophiles mesophiles psychrotrophs thermophiles hyperthermophiles

mesophiles

Unlike sugar, proteins provide which of the following elements? nitrogen carbon hydrogen oxygen

nitrogen

Some microorganisms can convert nitrogen gas (N2) to ammonia in a process called _______. nitrogen assimilation denitrification nitrogen fixation nitrification

nitrogen fixation

Aerotolerant anaerobes are also called _____ fermenters because they can only produce energy via fermentation.

obligate

An _____ aerobe, or strictly aerobic organism, requires O2 for survival.

obligate

Which of the following describes a microbe that must have O2 to survive? obligate aerobe passive aerobe semi aerobe facultative aerobe

obligate aerobes

Bacteria that cannot multiply if O2 is present, and are often killed by even brief exposure to air, are termed _____ _____

obligate anaerobes

If you inoculated a test tube of cooled liquid agar with an obligate anaerobe and incubated it, where would you expect to find growth? only at the bottom of the tube throughout the tube only at the top of the tube

only at the bottom of the tube

A species grows most rapidly at its ___ growth temperature.

optimum

Animals could not survive without autotrophs because without them the world would run out of ______. organic carbon inorganic nitrogen inorganic carbon organic nitrogen

organic carbon