chap 7 microbio

process most prokaryotes use to divide?

binary fission

process do certain fungi and some bacteria divide?

asexual budding

how many bacteria would be present after 3 hours if you start with a single bacterium that can divide every 30 minutes?

64

four phases of bacterial growth

1. lag phase- cells adjust to their environment, cells alter their gene expression in respnse to new setting, population growth is not usually seen.

2. Log phase: exponential cell growth, phase lasts as long as sufficient nutrients are available and metabolic wastes are not appreciably accumulating. 

3. Stationary phase: number of cells dividing = number of cells dying, length of phase depends on factors such as amount and type of nutrients in the culture and species being grown. 

4. Death phase: cells die as waste accumulates and nutrients are depleted. 

 Which type of bacteria grows at human body temperature (37^oC). Note: Therefore, many bacterial pathogens that infect humans are categorized in this range.

mesophiles

Observe the temperature ranges of thermophiles and extreme thermophiles; Using this information, what do you think the term thermophile means? (or look up the scientific terms thermo- and -phil(e)) 

tthermos=heat & philes= lover of

List the names and pH ranges for prokaryotes grouped by pH requirements. 

 Acidophiles pH 1 (or less) – pH 5. Neutralophiles pH 5-8. Alkaliphiles pH 9-11

What type of bacteria would you expect to find living in the Great Salt Lake of Utah?

halophiles

extremophile

organisms that live in extremes of pH, temperature and/or sald and that are exposed to a combination of stresses.

Many aerobic bacteria remediate reactive oxygen species (ROS) using enzymes that convert the reactive intermediates into nonreactive products. What reaction does the enzyme catalase perform? What reaction does the enzyme superoxide dismutase perform?

Superoxide dismutase converts superoxide to hydrogen peroxide (H202), then the enzyme catalase converts H202 into oxygen and water

The degree to which an organism can detoxify reactive oxygen species (ROS) is directly related to how much oxygen it can tolerate. Which of the following organisms do you think has no ability to detoxify ROS?

obligat anaerobe

There are two categories of organisms based on how they obtain organic carbon. How do heterotrophs obtain carbon? How do autotrophs obtain carbon?

 Heterotrophs are organisms, such as humans, that cannot fix carbon; they require an external source of organic carbon in order to live and grow. Autotrophs: “self-feeding” organisms, such as plants and other photosynthetic organisms, that use carbon fixation to convert inorganic carbon into organic carbon

What do phototrophs use for energy? What do chemotrophs use for energy? 

Phototrophs use light, chemotrophs break down chemical compounds 

List three physical states of growth media and state the main use for each

 Liquid formats, also called broth media, are idea for growing large batches of microbes. Used to study certain metabolic properties of an isolated bacterium. Solid media are useful for isolating colonies and observing specific culture characteristics. They are also used to isolate bacteria into pure cultures using the streak plate isolation technique. The most common application of semisolid media is for the motility test to determine if an isolated specimen is able to move

Define complex media. Define defined media. Make sure you can determine if a media is complex or defined by its formulation

 complex media: also called enriched media; contain a mixture of organic and inorganic nutrients that are not fully defined; instead, they contain more complex ingredients like blood, milk, proteins, or yeast extract.

Defined media: specialized media that are formulated to allow us to visually distinguish one microbe from another based on how they metabolize media components.

media components such as beef heart extract, yeast extract, etc., this is the clue that identifies media as complex

Because, the batches of these extracts are made from hundreds of cow hearts, or liters of yeast culture. We do not know the exact composition of 100’s of cow hearts—we know in general, there will be certain proteins, fats, etc, but we do not know the exact amount of each component. Similarly, when extracting all components of yeast, we have a general idea of what components are in it, but we do not know the exact amounts of each component of yeast. A defined media will always have specific chemical components. Glucose (C₆H₁₂O₆) is always glucose. Chemical formulas like MgSO₄ will always be MgSO₄. NaCl will always be NaCl. Therefore, any media that contains only components that are specific known chemical formulas will be defined.

purpose of differential media

Specialized media that are formulated to allow us to visually distinguish one microbe from another based on how they metabolize media components 

Which agar media differentiates between microbes that can or cannot lyse red blood cells (RBCs), and if the microbe can lyse RBCs,

it distinguishes the extent to which they can do

Differentiate between alpha, beta, and gamma hemolysis. What do each look like? What do each indicate about their ability to lyse red blood cells? 

Alpha: term applied to bacteria that do not lyse RBCs and instead just oxidize hemoglobin, the oxygen-carrying component of blood; they turn blood agar a green color.

Beta: term applied to pathogens (such as streptococcus pyogenes) that make hemolysins and can therefore lyse RBCs and generate a yellow zone around colonies growing on blood agar.

Gamma: term applied to bacteria that do not lyse RBCs.

 Eosin methylene blue agar (EMB) is a selective and differential media. What kind of organisms does EMB select for? What ability are organisms differentiated by? 

 EMB is another common medium with selective and differential capabilities. It contains the dyes eosin and methylene blue, which limit Gram-positive bacterial growth, while allowing Gram-negative bacteria to grow. Helps differentiate among Gram-negative bacterial species based on their ability to ferment the sugar lactose

What type of organism would you be growing if you added thioglycolate to the media?

anaerobic

What is the purpose of utilizing the streak-plate technique?

 Identifying a pathogen in a sample is to separate it from other organisms in the sample

deifne colony

As cells divide, their population increases to form a mound of cells called a colony

 List three direct methods of counting bacteria. List three indirect methods of counting bacteria.

microscopic count, coulter counter or flow cytometer, viable plate count

What is the downside of using the turbidity measurement for enumerating bacteria?

Turbidity, measurement, dry weight, biochemical activity

What is the difference between disinfection and sterilization

 Disinfection: decontamination measure that reduces microbial numbers. Sterilization: decontamination measure that eliminates all bacteria, viruses, and endospores

What is decimal reduction time (DRT)

The time in minutes that it takes to kill 90 percent of a given microbial population at a set temperature  

thermal death time

the shortest period of time that a given temperature must be held to kill all microbes in a sample

thermal deat point

The minimum temperature needed to kill all microbes in a sample within ten minutes

What process uses heat, steam, and pressure to sterilize microbial media and lab instruments?

Autoclave

Boiling water for 5 minutes kills which types of microbes? What does boiling water not destroy? 

Eliminates most pathogenic bacteria, protozoans (such as cryptosporidium and giardia that are found in most bodies of water), and viruses, but some endospores can withstand hours of boiling. Effective decontamination strategy, not efficient sterilization method. Heat-resistant objects like glassware or metal tools can be decontaminated (but not sterilized) by submerging them in boiling water for 10 to 20 minutes 

What process used by the dairy industry reduces the number of bacteria in milk? 

pasteurization

What type of sterilization is used when a microbiologist flames an inoculation loop using a Bunsen burner? 

dry heat

What microbial decontamination method is utilized when using a LifeStraw?  

filtration

What is the difference between disinfectants and antiseptics?

 Disinfectants: germicides used to treat inanimate objects.

Antiseptics: a class of germicides that are applied to living tissue such as skin

What is the difference between microbiocidal and microbiostatic germicides? 

Microbiocidal: term applied to germicides that kill microbes.

Microbiostatic: term applied to germicides that inhibit microbial growth, but do not kill microbes. 

What is the mode of action of alcohols such as ethanol or isopropanol

Target proteins and lipid membranes 

The disinfectant Lysol contains what type of chemical?

phenols

What is one of the most widely used halogen disinfectants? 

Chlorine bleach (sodium hypochlorite) 

Detergents are amphipathic molecules. What does that mean?

 This chemical feature allows them to remove water-soluble and water-insoluble substances, which makes them good cleaning agents

Which two chemical agents kill Mycobacterium? 

Glutaraldehyde or hydrogen peroxide 

How are naked viruses usually inactivated?

chlorine based agents

how are prions eliminated?

Eliminated through a combination of chemical treatments and increased temperature and pressure during autoclaving