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Flashcards in ch 6 Deck (23):

Pure culture (agar) –Koch and Hesse

A single, genetically homogeneous strain of a single species.

can be grown in liquid or solid media
used to examine growth rates & microbial biochemistry
useful for separating mixtures of different organisms


Isolation streaking

using an inoculation loop to dilute cells


serial dilutions with spread plate for counting viable colonies



Synthetic (minimal) media vs. Complex (rich) media vs. enriched media

synthetic-Water, salts, carbon, nitrogen, and energy sources added in precise amounts

complex-Nutrient-rich but poorly defined
Yeast/beef extract, peptides, vitamins whose exact concentration and composition is not known

enriched-For particularly fastidious organisms, blood or blood components added to a basic complex medium


Selective vs. differential media (can be both at times)

Selective media favor the growth of one
organism over another.

Differential media expose biochemical differences between 2 species that grow equally well.


Bacteria divide by binary fission

Binary fission is one parent cell splitting into two equal daughter cells.

Binary fission can be symmetrical or asymmetrical.

Caulobacter, Hyphomicrobium reproduce by budding

Eukaryotic microbes divide via mitosis


Know the 4 phases of microbial growth

1. lag phase
2. log or exponential phase
3. stationary phase
4. death phase


Know that gram staining should be done in the log phase of growth to yield proper results



Know terminology and environmental requirements:
Psycrhophiles (cold temp.)

grow at temperatures as low as 0° C but their optimum growth temperature is around 14° C.


Know terminology and environmental requirements:
Mesophiles (intermediate including body temp.)

have optimal growth between 20–40°C, with a minimum of 15°C and a maximum of 45°C.


Know terminology and environmental requirements:
Thermophiles (hot temp.) and Hyperthermophiles or Extreme thermophile

Thermophiles have adapted to growth at high temperatures, typically at 55°C and higher.

Hyperthermophiles can grow at temperatures as high as 121°

Extremophiles are bacteria, archaea, and some eukaryotes that can grow in extreme environments.


Barophiles –high pressure

Organisms that have adapted to grow at high pressures are called barophiles


Halophiles—high salt

Species that have evolved to require high salt (NaCl) concentrations are known as halophiles.


Acidiophiles (acid, low pH)

are bacteria and archaea that live in acidic environments. They are often chemoheterotrophs that oxidize reduced metals and generate strong acids such as sulfuric acid.


neutalophiles (neutral pH around 7)

are bacteria that generally grow between pH 5 and 8 and include most human pathogens


alkaliphiles (alkaline or basic, high pH)

occupy the opposite end of the pH spectrum, growing best at values ranging from pH 9 to pH 11



Some bacteria (aerobes) use oxygen as a terminal electron acceptor in the electron transport chain to extract energy trapped in nutrients and convert it to a biologically useful form

-Strict aerobes
are organisms that not only exist in oxygen but also use oxygen as a terminal electron acceptor. They grow only when oxygen is present and consume oxygen during metabolism.

Aerobes, but not anaerobes, destroy ROS with the aid of enzymes



For many bacteria (anaerobes), including several important pathogens, oxygen is toxic

Strict anaerobes
die in the least bit of oxygen. They do not use oxygen as an electron acceptor and die because they are vulnerable to the highly toxic, chemically reactive oxygen species produced by their own metabolism when exposed to oxygen. Reactive Oxygen Species (ROS) are oxygen molecules or ions with one too few or two many electrons.


facultative anaerobes

Facultative anaerobes that possess the enzymes to detoxify oxygen radicals and also the machinery for both fermentation and aerobic respiration



Aerotolerant anaerobes use only fermentation to provide energy but contain superoxide dismutase and catalase or peroxidase to protect them from ROS


microaerophiles—where would you find them in a tube?, which would you find in a puncture wound vs. a superficial wound?

will grow only at low oxygen concentrations. They possess a decreased level of superoxide dismutase and/or catalase


What are biofilms?

a mass of bacteria that stick to and multiply on a solid surface, such as a stone in a lake or a lung in a cystic fibrosis patient.



are resistant to many environmental stresses that kill vegetative cells