BIO 220: Lecture Exam #1 Part 2

Covers Ch 2

they use basic senses like sight, smell, hearing, and touch to observe and differentiate their experimental subjects

How do biologists who study large organisms typically observe their subjects?

because they are visible and can be directly observed using basic senses

Why is it easier for biologists to track growth and development in large organisms?

they work with microscopic organisms that are invisible to the naked eye

What challenges do microbiologists face when studying their subjects?

no

Are microscopic organisms visible to the naked eye?

they use carefully practiced techniques to collect and maintain microscopic organisms

How do microbiologists collect and maintain their experimental subjects?

for proper collection and evaluation

Why are techniques important in microbiology?

Inoculation, incubation, isolation, inspection, identification

What are the “Five I’s” in microbiology?

to locate, manipulate, grow, observe, and characterize microbes after specimen collection

What is the purpose of the Five I’s?

yes (they are ubiquitous)

Are microbes found everywhere in nature?

body fluids and tissues (humans and animals), water, soil, foods, inanimate objects (fomites)

What are common sources of microbial specimens?

nonliving objects that can carry microbes

What are fomites?

humans, animals, soil, water

What are considered reservoirs of infection?

serve as continual sources of infectious and noninfectious microbes

What do reservoirs of infection do?

yes

Do institutions have specific guidelines for sample collection and delivery?

for valid and timely lab test results

Why is proper sample collection and handling important?

proper technique, correct container, correct labeling, prompt transport to lab

What are four key requirements for proper sample collection?

with universal precautions (as if hazardous/infectious)

How should all specimens be handled?

blood, cerebrospinal fluid, sputum, urine, feces, diseased tissue

What are examples of clinical specimens?

swab, syringe, transport container

What devices are used to collect clinical specimens?

sterile

What must all collection instruments be?

adding a sample (inoculum) into or onto media

What is inoculation?

nutrient material that supports microbial growth (specimen-specific)

What is media (medium)?

sterile

What must all inoculation instruments and media be?

aseptic techniques

What technique must be used during inoculation?

placing inoculated media in controlled conditions

What is incubation?

temperature, moisture, light, oxygen

What conditions are regulated during incubation?

incubators

What equipment is used for incubation?

hours, days, or weeks (depends on organism)

How long does incubation usually last?

environmental conditions and nutrient media

What two factors are needed to support microbial growth during incubation?

a culture (visible microbial growth)

What does incubation produce?

in the broth (free-floating cells)

Where does microbial growth occur in liquid media?

cell replication

What does turbidity in liquid culture indicate?

no cell replication (sterile)

what does clear liquid media indicate?

on the surface (as colonies)

Where does microbial growth occur on solid media?

cell replication

What does surface growth on agar indicate?

sterile (no microbial growth)

What does no surface growth on an agar plate indicate?

pure culture, mixed culture, contaminated cultures

What are the three main types of cultures?

growth conditions, selection, or manipulation errors

What are the three incubation culture types based on?

growth of only a single known species

What is a pure culture?

by subculture

How is a pure culture usually created?

contains two or more identified species

What is a mixed culture?

contains unwanted microorganisms of unknown identity (contaminants)

What is a contaminated culture?

yes

Are most clinical specimens considered contaminated?

due to natural variation in microbe types

Why are most specimens considered contaminated?

separating one species from another

What is isolation in microbiology?

no (it’s rare)

Is it common to collect only one microbe type in nature?

it grows into a colony

What happens when a single bacterial cell is given space on nutrient media?

a macroscopic cluster of cells appearing on a solid medium arising from the multiplication of a single cell

What is a colony?

cells just from that species

If a colony forms from a single cell, what type of cells does it contain?

streak plate (most common), loop dilution, spread plate

What are three common isolation methods?

streak plate method

What is the most commonly used method to get pure cultures?

sterile inoculating loop

What tool is used in the streak plate method?

loop is dipped once into culture and streaked over nutrient medium in a pattern

How is the streak plate performed?

final cells are spread far enough apart to grow into isolated colonies

Why does the streak plate method work?

when the target organism is in large numbers

When does the streak plate method work best?

once

How many times is the loop dipped into the culture in the streak plate method?

sterilized (heat flamed)

What must be done to the loop after each streak series?

pour plate method

What is another name for the loop dilution method?

sample is inoculated into a series of liquid agar tubes to dilute the number to cells in each successive tube

How is the loop dilution method performed, and why are multiple tubes used?

the agar is poured into sterile Petri dishes and allowed to solidify

What happens after inoculating the tubes in the loop dilution method?

a small volume of diluted sample is pipetted onto the surface of solid medium

What is the spread plate method?

evenly with a sterile spreading tool

How is the sample spread in the spread plate method?

no

Is the spread plate method ideal for quick isolation?

observing the characteristics of microbial growth

What is inspection in microbiology?

colony or broth growth—color, texture, size

What is observed macroscopically during inspection?

motility, cell shape, cell size

What is observed microscopically during inspection?

microscope (using prepared slides)

What tool is used for microscopic inspection?

staining techniques

What can be used to enhance microscopic observation?

data from inspection

What does identification build off of?

morphology is often similar among microbes

Why are further tests needed beyond inspection?

physiological tests and assays

What types of tests are commonly used for accurate identification?

phenotypic, genotypic, immunologic

What are the three main types of identification methods?

characterization of cellular metabolism (biochemical tests, media reactions)

What does phenotypic testing examine?

products of growth (alcohol, gas, acids), enzyme presence, energy mechanisms

What are examples of phenotypic traits tested?

genetic characteristics (DNA analysis)

What does genotypic testing examine?

immunological characteristics; serology (antigen-antibody interactions)

What does immunologic testing examine?

COVID-19 rapid antigen test

What is an example of an immunologic test?

stock cultures—preserved, pure samples stored for long-term use

How are cultures maintained for future use?

sterilized and properly destroyed

What must be done with unused cultures?

metric system

What system is used to measure in microbiology?

meter (m)

What is the standard unit of length in the metric system?

by factors of 10

How are metric units related to each other?

meters (m) and centimeters (cm)

What units are used to measure macroscopic organisms?

micrometers

What unit is used to measure most microbes?

nanometers (nm)

What unit is used to measure microbial structures?

10^-6 meters

How big is a micrometer?

10^-9 meters

How big is a nanometer?

magnification, resolution, contrast

What three qualities make a microscope effective?

visible (white) light

What type of light does light microscopy use?

to observe specimens

What is the purpose of light microscopy?

compound light microscopy, darkfield microscopy, phase-contrast microscopy, differential interference contrast microscopy, fluorescence microscopy, confocal microscopy

What are the types of light microscopy?

interaction between light rays and lens curvature

What causes magnification in a microscope?

experiences refraction (bending)

What happens to light as it passes through a lens or water?

refracted light creates an image when an object is lit and placed at the right distance

How is an image formed?

the degree to which the image is enlarged

What is the power of magnification?

compound light microscope

What type of microscope is most common in biology classes?

2

How many sets of lenses does a compound light microscope use?

light rays come from an illuminator (light source), passes through a condenser (lens system located below the stage that directs light rays through the specimen), light rays then pass into the objective lenses (lens closest to the specimen), light rays then pass into ocular lens (eyepiece)

What are the 4 steps in magnification?

compound magnification (occurs in two phases) - objective lens and ocular lens

What type of magnification does a compound microscope use?

real image

What does the objective lens form?