microbio exam 3

microbial growth

cell division that repoduces new (daughter) cells and increases cell population

can be studied in controlled lab settings but we can only grow 1% of all known bacterial species

binary fission

cell reproductive option

cell replicates DNA, creates chromosomes, and pinches along the middle to divide

budding

cell reproductive option

new growth forms on one end of a cell and is eventually sealed off while remaining attached to the cell

spore forming

cell reproductive option

cells extend long hyphae out while “spore” cells divide out from the ends and detach

generation time

the time it takes for a species of cell to divide

1 cell becomes 2, then 4, then 8, etc in exponential growth

calculated by (growth time in minutes) ÷ (# of generations)

lag phase

first distinct growth phase that occurs when using a closed pure batch system

cells adjust to new environment and may not divide much

log phase

second distinct growth phase that occurs when using a closed pure batch system

if environment is good/optimal, bacteria will divide exponentially (steep population growth)

stationary phase

third distinct growth phase that occurs when using a closed pure batch system

as nutrients are depleted and metabolic waste accumulates, the population reaches a plateau

the number of cells dividing = the number of cells dying

death phase

fourth and final distinct growth phase that occurs when using a closed pure batch system

cells start dying and population declines. some individuals survive on adapting and feeding on dead cell remains

less steep population decrease

extreme thermophiles

temperature growth requirement scale

can survive/thrive in MUCH hotter than human body temperature (98.6)

thermophiles

temperature growth requirement scale

can survive/thrive in hotter than human body temperature (98.6)

mesophiles

temperature growth requirement scale

can survive/thrive in temperatures similar to the human body (98.6)

most pathogens

psychrotrophs

temperature growth requirement scale

can survive/thrive in colder than human body temperature (98.6)

psychrophiles

temperature growth requirement scale

can survive/thrive in MUCH colder than human body temperature (98.6)

acidophiles

pH growth requirement scale

prefer acidic pH levels (lower concentration of OH^- molecules)

neutrophiles

pH growth requirement scale

prefer neutral pH levels

most pathogens

alkaliphiles

pH growth requirement scale

prefer basic (alkaline) pH levels (higher concentration of OH^- molecules)

halophiles

most microbes require moderate salinity BUT halophiles are adapted to HIGH SALT environments

obligate anaerobes

oxygen growth requirements (microbes vary in how they use/don’t use oxygen)

cannot survive survive in aerobic environments; can not use oxygen

obligate aerobes

oxygen growth requirements (microbes vary in how they use/don’t use oxygen)

require oxygen for survival; can use oxygen

facultative anaerobes

oxygen growth requirements (microbes vary in how they use/don’t use oxygen)

prefer osygen but can survive without it

nutrients

elements (carbon, nitrogen, oxygen, etc) required for growth and energy

autotrophs

can generate energy with nutrients via sunlight

heterotrophs

must get energy and nutrients from other organisms, often by consuming them

growth factors

organic molecules (amino acids, vitamins, nitrogenous bases, etc) are required for growth; some microbes cannot make these themselves and require them from a host

liquid

physical culture media

these are broth media and are ideal for growing large quantities of microbes

solid

physical culture media

substances like agar, which are useful for isolating colonies

semisolid

physical culture media

less dense agar that lets microbes penetrate deeper into the substance

defined media

chemical composition culture media

synthetic substance where we know all the ingredients and their concentrations; more specific

complex media

chemical composition culture media

mixture of many substances (blood, milk proteins, yeast extract) where we don’t know the precise concentration of all ingredients; less specific

differential media

functional culture media

allows growth of multiple species of microbes but provides visual indication to distinguish the species

selective media

functional culture media

encourages growth of a specific target microbe while containing substances that inhibit the growth of others

streak plate technique

way of quantifying microbes

microbial culture is diluted on an agar plate so that separate colonies (tiny mounds) will grow on the surface

use an inoculating loop to spread culture streaks at 90 degree angles around the plate; or use counting chamber

flow cytometer

way of quantifying microbes

add fluorescent molecular “labels” to a specific kind of microbe. as you pass a sample of cells through a tube, a laser shoots through the tube, and a detector determines if the light that passes through comes from fluorescent-tagged cells

spectrophotometer

indirect way of quantifying microbes

machine shoots light through a liquid sample and measures turbidity (how cloudy) the sample is → the cloudier the sample, the more cells/microbes are present

disinfection (D) vs. sterilization (S)

various levels at which we decrease the population of microbes; physical agent

D→ reducing microbial numbers

S→ eliminating all bacteria, viruses, endospores, etc

refrigeration

come back to this

dry heat

physical agent

S→ incineration or hot air ovens @ sufficient temp will dehydrate and kill most microbes

moist heat (D)

physical agent

D→ boiling and pasteurization will kill many microbes

moist heat (S)

physical agent

S→ autoclaving AKA applying steam heat with intense pressure will sterilize

radiation

physical agent

high energy electromagnetic waves

ionizing radiation

physical agent

S→ gamma rays and x-rays that generate reactive ions that kill microbes

non-ionizing radiation

physical agent

D→ UV rays that denature DNA, leading to severe mutations and often cell death

filtration

mechanical removal

barrier with tiny pores that lets air or liquid molecules pass through, but microbes or viruses

D→ air filter (ex: HEPA)

S→ liquid membrane filters (ex: cellulose nitrate)

alcohols

chemical agent

D→ organic molecules with an OH^- group that denature proteins and break down liquid membranes

aldehydes

chemical agent

S→ similar to alcohols, but the O is by itself and acts to denature cellular structures

ex: formaldehyde

phenols

chemical agent

D→ specialize in breaking down bacterial cell walls (ex: used in personal hygiene items, like mouthwash, soap, and lysol disinfectants)

halogens

chemical agent

D→ act to oxidize cellular components (ex: chlorine, iodine, etc)

detergents

chemical agents

D→ amphipathic molecules (can attach to both hydrophobic and hydrophilic substances and are then washed away)

ex: dawn dish soap

infectious disease

illness caused by a pathogen

true pathogen

do not require weakened hosts

opportunistic pathogen

only cause disease when they shift locations or the host is weakened in some way

endemic infections

routinely occuring infections (ex: common cold)

sporadic infections

isolated events (ex: ebola outbreak)

epidemic vs pandemic

e: widespread disease outbreak

p: multiple countries

zoonotic diseases

spread from animal to humans

most are noncommunicable (don’t spread from person to person) but some can mutate into communicable forms

subjective vs objective

during active infection, a patient can show objective indicators (fever, blood in stool) or subjective indicators (pain, fatigue)

reservoir

habitat where pathogen is naturally found (soil, water, inside an organism)

source

means of pathogen disseminating from reservoir to new hosts

exogenous source

source outside the host

endogenous source

sourse within the host

direct contact transmission

host comes into physical contact with source of pathogen

vertical transmission

special tyoe of direct contact transmission where pathogen passes from mother to offspring during pregnancy, childbirth, or breast feeding

indirect contact transmission

pathogen spreads without physical contact with source

airborne

type of indirect contact transmission

pathogen enters through respiratory route. these spread via respiratory droplets or smaller aerosols

vehicle

type of indirect contact transmission

pathogen spreads via contaminated substance/surface

vector

type of indirect contact transmission

pathogen spreads via an organism that carries it to the host

incubation period

first stage of infectious disease

time between infection and earliest symptoms; could be hours for one disease and years for another

prodromal phase

second stage of infectious disease

patient experiences first symptoms which are often not severe

acute phase

third stage of infectious disease

patient experiences full-blown and most severe version of symptoms associated with disease (this is a symptomatic case)

it is possible for someone to move through these stages with mild or none-existent symptoms (this is an asymptomatic case)

patient is most likely to die in this stage

period of decline

fourth stage of infectious disease

pathogen replication decreases and symptoms decline

convalescent period

fifth (and final) stage of infectious disease

pathogen is eliminated or declines to normal/healthy levels. some pathogens may remain and become dormant

epidemiology

study of how diseases occur in populations of people

goals: describe nature, cause, and extent of diseases; intervene to protect and improve health in populations

epidemiological triangle

the “who”/”what”?”where” of a disease

includes environmental, host, and etiological factors

host factors

aspect of epidemiological triangle

health, sex, age, ethnicity, life, etc of host individual

environmental factors

aspect of epidemiological triangle

climate, water source, geographic location, etc

etiological factors

aspect of epidemiological triangle

type of agent (bacteria, virus, parasite, prion, fungus, etc)

quarantine

person with infection (or potentially infected) undergoes a period of confinement away from the general population

wait for potential incubation period to pass to see if symptoms occur

vectors

agents that spread pathogens