Microbiology Lab Exam I

The skin is generally a(n) [blank_start]inhospitable[blank_end] environment for most microorganisms.

Whare are some protential invasive avenues for pathogens through the skin?

What are some traits of human skin that make it inhospitable to most microbes?

Human skin acts as an efficient protective barrier by making a hostile environment that no microbes can live on.

More bacteria are found in moist areas, such as the [blank_start]armpit[blank_end], than on the dry surfaces of the [blank_start]arms/legs[blank_end].

Examples of normal flora include:

What are transient microorganisms?

What is an etiological agent?

The significance of bacteria as etiological agents was documented by [blank_start]Robert Koch[blank_end] in [blank_start]1876[blank_end].

Handwashing is generally considered the [blank_start]most[blank_end] important procedure for stopping infections and the spread of germs, but excessive handwashing can actually be [blank_start]detrimental[blank_end] effects.

The main goals of smearing are:

[blank_start]Simple stain[blank_end]: uses a single stain or dye to color bacterium. [blank_start]Gram stain[blank_end]: differentiates organisms according to cell wall structure. [blank_start]Endospore stain[blank_end]: differentiates endospores and vegetative cells with differential staining. [blank_start]Acid-fast[blank_end]: useful for waxy cells that may not be easily stained by other procedures.

Basic dyes are [blank_start]positively[blank_end] charged, containing [blank_start]cationic[blank_end] chromophores. Because the bacterial cells are slightly [blank_start]negatively[blank_end] charged, there is an attraction between the [blank_start]positive[blank_end] dye and the [blank_start]negative[blank_end] cell. Acidic dyes are [blank_start]negatively[blank_end] charged, containing [blank_start]anionic[blank_end] chromophores, and do not stain bacterial cells.

Examples of basic dyes are:

Examples of acidic dyes are:

Label the parts of the microscope.

Match the growth media with their physical forms: [blank_start]Broths[blank_end]: liquid [blank_start]Deeps[blank_end]: semi-solid [blank_start]Petri Dishes and Slants[blank_end]: solid

What is the most common solidifying agent used in growth media?

What is agar?

Agar contains key nutrients for bacteria, which is why it is used in growth media so often.

[blank_start]Aseptic[blank_end]: without contamination [blank_start]Septic[blank_end]: without any microbe growth

Tools used for inoculation must be [blank_start]sterile[blank_end], but the inoculation itself must be carried out by [blank_start]aseptic[blank_end] technique.

A petri dish must be labeled with:

Petri dishes should be labeled on the [blank_start]bottom[blank_end], and stored agar side [blank_start]up[blank_end].

The best way to attain isolated colonies on a petri dish is by using the [blank_start]four[blank_end]-way streak technique.

Gram staining causes gram-positive cells with a [blank_start]thick[blank_end] peptidoglycan layer to stain [blank_start]blue to purple[blank_end] and gram-negative cells with a [blank_start]thin[blank_end] peptidoglycan layer to stain [blank_start]red to pink[blank_end].

Label the morphology forms:

Label the morphology elevation terms:

Label the margins:

What are endospores?

Endospores serve as a protective structure for survival of the organisms.

Endospores possess a permeability barrier that prevents dyes from entering unless the barrier is destroyed.

An endospore is structurally and chemically [blank_start]more[blank_end] complex than the vegetative cell it comes from. Externally, there are [blank_start]more[blank_end] layers.

What makes the endospore chemically unique?

Endospores are often called metabolically active.

Check traits of the cortex of the endospore:

A chemically-defined ([blank_start]synthetic[blank_end]) medium is one in which the exact chemical composition [blank_start]is[blank_end] known. A complex ([blank_start]undefined[blank_end]) medium is one in which the exact chemical constitution of the medium [blank_start]is not[blank_end] known.

When is a defined medium a minimal medium?

What is a selective medium?

[blank_start]Selective[blank_end] medium: has components to inhibit growth of some bacteria and promote growth of desired bacteria. [blank_start]Differential[blank_end] medium: allows investigator to distinguish between different types of bacteria based on pattern of growth

What is an enrichment medium?

When is an enrichment medium the best option?

Which of these are chemically defined mediums?

Which of these are complex mediums?

[blank_start]Psychrophiles[blank_end]: can grow at 0 degrees, but optimally near 37 degrees [blank_start]Mesophiles[blank_end]: optimum temperature near 37 degrees [blank_start]Thermophiles[blank_end]: optimum temperature about 45-70 degrees [blank_start]Extreme Thermophiles[blank_end]: optimum temperature 80 degrees or higher

How are psycrophilic bacteria adapted to a cool environment?

How are thermophiles adapted to warmer environments?

[blank_start]Obligate aerobes[blank_end]: require O2 for growth [blank_start]Obligate anaerobes[blank_end]: do not need O2, in fact, it is toxic to them [blank_start]Facultative anaerobes[blank_end]: can switch between aerobic and anaerobic types of metabolism [blank_start]Aerotolerant anaerobes[blank_end]: strictly anaerobic, but can tolerate presence of O2