Topic 3: Microbes in the Environment

Bacteria

________ that is inoculated on media will increase in number during an incubation period.

Chemically defined medium

a medium whose exact chemical composition is known

Complex media

media for which the exact chemical composition varies slightly from batch to batch

Nutrient broth

commonly used liquid complex medium

Nutrient agar

when agar is added to a nutrient broth medium and becomes a solid medium

Inoculated

intentionally introduced

Colony

population of cells that arises from a single bacterial cell,

Colony-forming unit

a colony that may arise from a group of the same microbes attached to one another

True or False: Microbes are found only in select environments.

False - found everywhere

Are most microbes harmful or harmless?

harmless

What must be provided in a medium for culturing bacteria?

macronutrients, an energy source, and growth factors

What is a chemically defined medium?

a medium whose exact chemical composition is known

What media is most chemoheterotrophic bacteria grown on?

complex media

What is complex media?

media where exact chemical composition varies slightly from batch to batch

What are peptones?

organic carbon, energy, and nitrogen sources supplied by a protein in the form of meat extracts and partially digested proteins

What is the commonly used liquid complex medium?

nutrient broth

When agar is added to a nutrient broth, what does it become?

nutrient agar

What is agar an extract from?

marine red algae

Agar liquefies at ___ and remains in a liquid state until cooled to ___. Once solidified, it can be incubated at temperatures of up to ___ and remain solid.

100 °C, 40 °C, 100 °C

Once a media is prepared, what must occur afterwards?

sterilization

What is the most common method of sterilization?

steam sterilization or autoclaving

What is the process of autoclaving? (temp, pressure, time)

heated to 121 °C at 15 lbs of pressure (15 psi) for 15 minutes

What is the benefit of petri plates?

provide a large surface area for examination

What does the term inoculated mean?

intentionally introduced

When bacteria is inoculated on a media, the number ___ during incubation.

increase

Liquid media becomes ___ or cloudy during bacterial growth.

turbid

What is a colony?

population of cells that arise from a single bacterial cell

What is a colony-forming unit?

a colony that may arise from a group of the same microbes attached to one another