Microbial Growth

Nutrition is the process by which chemical substances are _____ from the environment and used for __________. Essential nutrients are _____ to an organism and cannot be _____ by the orgnanism

acquired; cellular activities; provided; made

Macronutrients are required in __________ and play principal roles in __________ and _____. Micronutrients are required in __________ and are involved in __________ and __________

large quantities; cell structure; metabolism; small amounts; enzyme function; maintenance of protein structure

Microbial growth is the _____ in __________. Populations increase at a very _____ rate and colonies of bacteria contain billions of cells. The method of growth is __________ and the typical growth rate is _____ minutes

increase; cell number; rapid; binary fission; 20-30

Steps fo binary fission:

1. Cell elongates and DNA is replicated

2. Plasma membrane begins to constrict and new wall is made

3. Cross wall forms completely separating the two DNA copies

4. Cells separate

The time required for a complete fission cycle is called _____. Each cycle increases the population by a factor of ____________

generation/doubling time; 2 - exponential or logarithmic growth

Bacterial growth curve:

1. Lag phase: intense activity preparing for population growth but no increase in population

2. Log phase: logarithmic or exponential growth

3. Stationary phase: period of equilibrium where microbial death balances production of new cells

4. Death phase: population is decreasing at a logarithmic rate

Direct count with counting chamber: Volume of a bacterial suspension placed on a slide, this is called __________. The __________ of bacteria per viewing field is calculated

Petroff-Hausser cell counter; average number

Viable count using plate count method: Bacteria is collected in a tube and a series of _____ is performed. The bacteria is grown on plates for each tube, and the general rule is that you want about _____ colonies. You are only looking at _____ cells

dilutions; 30-300l viable/living

Viable count using membrane filtration method: A _____ is used on a plate to grow _____ colonies

filter; specific

Indirect count using a spectrophotometer: A light source __________ through specimen and the spectrophotometer measures the light that is transmitted as a _____

transmits light; percent

Environmental factors that affect microbial growth:

temperature, pH, osmotic pressure, carbon, nitrogen, sulfur, phosphorus, trace elements, oxygen, and organic growth factors

Psychrophiles tend to be _____ organisms that prefer _____ to _____ ºC

archaic; -5; 15

Psychrotrophs prefer _____ to _____ ºC but will grow in the _____

20; 30; refrigerator

Mesophiles prefer _____ to _____ºC. Temperatures similar to __________

25; 40; humans/room temperature

Thermophiles prefer _____ to _____ ºC

50; 60

Hyperthermophiles prefer _____ ºC and tend to be _____ organisms

>80; archaic

Food preservation temperatures:
-30-0ºC has _____ significant growth below freezing.

0-5ºC are refrigerator temperatures that may allow __________; very few _____

5-15ºC are temperatures where many __________

15-50ºC allows of rapid growth of _____ and some may produce _____

50-60ºC allows for very _____ bacterial growth

60ºC+ are temperatures that _____ most microbes although lower temperatures take more time

no; slow growth of spoilage bacteria; pathogens; bacteria grow; bacteria; toxins; slow; destroy

pH requirements:

Extreme acidophiles _____

Acidophiles (ex. mold, yeast) _____

Neutrophiles _____

Alkalophiles _____

Extreme alkalophiles _____

0-2

2-5

6-8

9-11

12-13

Effects of osmotic pressure:

Hypertonic environments cause _____

Hypotonic environments cause _____

Obligate (extreme) halophiles are specialized microorganisms that strictly require __________to survive, grow, and maintain cell structure

Facultative halophiles don’t require __________ but still tolerate high osmotic pressure

plasmolysis; osmotic lysis; high salt concentrations; high solute concentration

Carbon plays a role in __________ and is a __________. Chemoheterotrophs use organic carbon sources to _____ energy and photoautotrophs use CO2 to obtain energy through _____

structural components; source of energy; obtain; photosynthesis

Nitrogen plays a role in __________ for _____ and _____. Some bacteria use _____ or _____ and a few bacteria use N2 for __________

structural components; proteins; nucleic acids; NH4+; NO3-; nitrogen fixation

Sulfur is found in __________. Most bacteria decompose _____ and some of them use _____ or _____. Phosphorus is found in _________ and _____ is a source of phosphorus. Trace elements are _____ elements required in small amounts

amino acids, thiamine, and biotin; proteins; SO42- or H2S; DNA, RNA, ATP, and membranes; PO43-; inorganic

Organic growth factors must be obtained from __________. _____ bacteria require many

the environment; fastidious

Toxic derivatives of oxygen:

Superoxide dismutase (SOD): removes _____

Catalase removes _____

Peroxidase removes _____

superoxide (oxygen free radicals); hydrogen peroxide; hydrogen peroxide

Obligate aerobes: only _____ growth

Facultative anaerobes: both _____ and _____ growth; greater growth in __________

Obligate anaerobes: only _____ growth; growth ceases in __________

Aerotolerant anaerobes: only _____ growth but growth continues in __________

Microaeropholes: only _____ growth; oxygen _____ in low concentrations

aerobic; aerobic; anaerobic; presence of oxygen; anaerobic; presence of oxygen; anaerobic; presence of oxygen; aerobic; required

With increased CO2, CO2 incubators __________ and is similar to __________. Candle jars _____ CO2 levels as the candle burning uses _____ and produces _____

control CO2 levels; conditions of the human body; increase; O2; CO2

Cultivation of anaerobes:

Anaerobic growth chambers combine __________

Anaerobic incubators have oxygen _____ with N2 gas

Anaerobic media uses _____

hydrogen with oxygen; replaced; thioglycollate broth