TCU Dr Jones Microbiology Final

prokaryotic cell with a rod shape

bacillus

spherical bacterial cell

coccus

spiral shaped bacteria

vibrios, spirilla, spirochete

Other shapes of bacterial cells

square, appendage, star-shaped, filamentous

Structure and organization are based on specific processes cells need to carry out:

Sensing/responding to stimuli, Compartmentation of metabolism, Growth and reproduction

Bacterial Flagella

are long appendages Extending from the cell surface used for cell motility

Anatomy of a bacterial flagella

helical filament, a hook, and a basal body

chemotaxis

moving up the concentration gradient of a chemical attractant

Pili

are protein fibers extending from the surface of many bacteria

Pili help the cell...

Attach cells to surfaces and form biofilms and microcolonies

conjugation pili are used to

transfer genetic material between cells

Glycocalyx

is an outer layer external to the cell wall that is an adhering layer of polysaccharides (sometimes small proteins)

capsule

A thick glycolayx bound to the cell

A slime layer

A thinner, diffuse layer of polysaccharides that protects cells from the environment, and allows them to attach to surfaces

bacterial cell wall

a tough and protective external shell made of peptidoglycan

The cell wall's functions

protects the cell from injury, and to maintain cell shape and water balance

Gram-Positive bacteria

have thick peptidoglycan cell walls containing teichoic acid

Gram-Negative bacteria

have a 2-dimensional peptidoglycan layer and no teichoic acid

Has an outer membrane, separated from the cell membrane by the...

periplasmic space

porins

in outer membrane, selectively allow small molecules into the periplasmic space

represents the interface between the cell environment and the cell cytoplasm

The cell membrane

The fluid mosaic model

It is a fluid layer of phospholipid and protein

...form a permeability barrier

Hydrophobic fatty acid chains in the phospholipids

Membrane proteins perform or aid in many functions

Cell wall synthesis, Energy metabolism, DNA replication, Sensation of stimuli, Molecule transport

Antimicrobial substances may...

...disrupt or dissolve the bilayer

Binary Fission

The cell doubles in mass, DNA replicated in the two strands separate

Cytokinesis

is an inward pinching of the cell membrane and cell wall to separate the cell into two genetically identical cells

The generation (or doubling) time

an interval between successive binary fissions

This constant doubling of the numbers only occurs as long as...

nutrients for growth are available during the log phase of growth

A bacterial growth curve

illustrates the dynamics of growth

During the lag phase

no cell division occurs while bacteria adapt to their new environment

The logarithmic (log) phase

exponential growth of the population occurs during this phase

Human disease symptoms usually develop during it

Log Phase

Stationary phase

when reproductive and death rates equalize

Decline (exponential death) phase

the accumulation of waste products and scarcity of resources causes it to enter

Endospores are a response to

nutrient limitation

Endospores are a highly resistant survival structure formed by species of _____ and _____ when nutrient supplies are low

Clostridium and Bacillus

Spores can lay dormant for years then germinate into a vegetative cell, withstand

boiling water, alcohol and radiation

A stressed cell undergoes asymmetrical cell division creating...

creating a small prespore and a larger mother cell

The prespore contains

Cytoplasm, DNA, Dipicolinic

Dipicolinic acid

stabilizes proteins and DNA

The mother cell matures the prespore into an

endospore

The endospore then

disintegrates, freeing the spore

Endospores abilities

Are resistant to desiccation, heat, and undergo very few chemical reactions

When environmental conditions are again favorable, the spore

protective layers break down and the spore germinates into a vegetative cell

Why are Spores so hard to kill

They are not metabolically inert, have a low water content, a thick spore coat, and contain lots of calcium and Dipicolinic acid (10% by weight). All thought to contribute to their heat resistance

The basic requirements for a bacteria to grow include

Water, Carbon/energy sources, Essential elements and organic growth factors, Temperature, pH, Oxygen, Carbon dioxide, Osmotic conditions

obligate aerobes

which require oxygen to grow

Microaerophilic

prefer oxygen slightly lower than air

Anaerobes

do not or cannot use oxygen

Aerotolerant

are insensitive to oxygen but can grow in its presence

Obligate anaerobes

are inhibited or killed by oxygen

Facultative prokaryotes

grow either with oxygen, or in reduced oxygen environments

Capnophilic bacteria

require an atmosphere low in oxygen and rich in carbon dioxide must incubate in a candle jar

Thioglycollate broth

can be used to test an organisms oxygen sensitivity

Heat

is one of the most common physical control methods

At temperatures above the growth range

Proteins and nucleic acids are destroyed, Water is removed, Thermal death time, Thermal Death Point

Thermal death time

each microbial species has a thermal death time for a given temperature

Thermal death point

The minimum temperature at which it dies in a given time period

Incineration

uses direct flame to kill microbes

Dry heat

requires long periods of exposure to high temperatures,

Moist heat

(like boiling water) is faster and effective at lower temperature than dry heat

How does Dry heat destroy the bacteria

The heat changes microbial proteins and removes water, slowly burning the microbes

How does Moist heat destroy the bacteria

It kills microbes by denaturing their proteins

Pressurized steam is used in an _______ to sterilize a variety of objects

Autoclave

The prevaccum autoclave decreases...

Cycle time, Exposure of sensitive, Material to steam

Fractional sterilization

is used for sterilization if material are not suited to the autoclave

Pasteurization

Reduces bacterial populations in food and drink and the chances of spoilage and disease. Bacterial spores are not affected by pasteurization

Filtration

Traps microorganisms as fluid passes through a filter, organisms above a certain size threshold are trapped in the pores

HEPA

High-efficiency particulate air filter

Ultraviolet Light

can be used to control microbial growth by causing thymine molecules to link together

What is impaired when UV light is used

Errors in protein synthesis and impairment of chromosome replication occur

X rays and Gamma rays (ionizing radiations)

force electrons out of microbial molecules, affects cell metabolism and physiology

Sterilization

involves destruction of all living microbes, spores, and viruses

Sanitation

reduces the numbers of pathogens or discourages their growth

Antiseptics

are used to destroy pathogens on living tissue

Sanitizing

means reducing microbial population to a safe level

Sepsis

refers to contamination by microorganisms

Degerming

means removing organisms from an objects surface

Antiseptics and Disinfectants have distinctive properties

Able to kill o r slow growth of microbes, Nontoxic to humans and animals, Soluble in water, Storable, substantial shelf life, Effective quickly and at low concentration, Not corrosive and instruments, Does not combine with organic matter, Easy to obtain and inexpensive

The phenol coefficient (PC)

indicates disinfecting ability compared to that of phenol

An in-use test

to compare samples of substrate before and after disinfection

2 Tests used to evaluate for antiseptic's effectiveness

phenol coefficient and in-use test

Phenol and Phenolic Compounds

denature proteins

Negative points of Phenol:

Is expensive, Is caustic, Has a pungent odor

Positive points of Derivatives

Have greater germicidal activity and have lower toxicity than phenol

Bisphenols

are combinations of two phenol molecules

Halogens

oxidize proteins

Chlorine

keeps bacterial populations low in municipal water supplies and swimming pools

Iodine

is used to disinfect wounds, water, and restaurant equipment

Iodophores

release iodine over a long period of time

Heavy metals

interfere with microbial metabolism

Mercury, copper, and silver

are reactive with proteins, disrupting cellular metabolism, killing microbes

Alcohols

denature proteins and disrupt membranes

Ethanol

is effective against vegetative cells but not spores

Membrane disruption is caused by

lipid dissolution

Soaps and Detergents act as

Surface-Active Agents

Soaps remove microbes by

emulsifying and solubilizing particles on the skin

Detergents

Are surfactants and they also cause cytoplasm leakage from microbial membranes

Quaternary ammonium compounds

react with cell membranes and destroy some bacteria and viruses