Micro exam 3

Microbial growth

Microbial growth

an increase in a population of microbes rather than an increase in size of an individual

Result of microbial growth

discrete colony

Discrete colony

an aggregation of cells arising from single parent cell

Polymerization reactions make what type of molecules

macromolecules which are used to make new structures

Binary fission in a rod-shaped prokayote

1. Parent cell prepares for division by enlarging its cell wall, cell membrane, and overall volume,

2. Septum begins to grow inward as the chromosomes move toward opposite ends of the cell (other cytoplasmic components are distributed to the two developing cells)

3. Septum is synthesized completely through the cell center, and the cell membrane patches itself so there are two separate cell chambers

4. Daughter cells are divided. Some species separate completely while others remain attached forming chains, doublets, or other cellular arrangements.

Cell replication happens in which phase

S-phase

Growth

increase in the number of cells

Binary fission

cell division following enlargement of a cell to twice its minimum size

Septum

partition between dividing cells, pinches off between two daughter cells

Generation time

time required for microbial cells to double in number

FtsZ

forms ring around center of cell; related to tubulin

Divisome complex

forms where the septum starts

Planktonic growth

growth as suspension

sessile growth

attached to a surface

Biofilms

attached polysaccharide matrix containing embedded bacteria

Microbial mats

multilayered sheets with different organisms in each layer

What are the four growth phases in a closed system

lag phase, exponential phase, stationary phase, and death phase

What is an advantage to a continuous culture in an open system

1. Cell population can be maintained in the exponential growth phase for long periods of time.

2. Repetition of experiments can be done with knowledge that the cell population used each time will be as close to being the same as possible

Ex. Chemostat

Procedure for viable counting using serial dilutions

Ex. Standard plate count

serial dilutions of the sample are plated until colonies on plates can be counted. Then you multiply by the dilution to get the total in sample

Indirect counting: Turbidity measurements of microbial growth

Usually uses light

Cardinal temperatures

the minimum, optimum, and maximum temperatures at which an organism grows

Membrane gelling

transport processes so slow that growth cannot occur

protein denaturation

collapse of the cytoplasmic membrane; thermal lysis

psychrophile

<10 degrees

Mesophile

range from 10-45 degrees

Thermophile

range from about 40-70 degrees

Hyperthermophile

>60 degrees

Psychrophiles like the cold

ex. many diatoms, green algae, and fungi

Microbial growth at cold temperatures requires what

Production of enzymes that function optimally in the cold

Features that provide more flexibility

• more alpha-helices than beta-sheets

• more polar and less hydrophobic amino acids

• fewer weak bonds

Transport processes function optimally at low temperatures due to modifications of cytoplasmic membranes

• High unsaturated fatty acid content

cold shock proteins

Where are hyperthermophiles found

Found around mineral deposits of silica and sulfur

Hyperthermophiles provide for other microbes and can be electron donors

Microbial growth at high temperatures

Enzymes and proteins function optimally at high temperatures (features that provide thermal stability)

• Critical amino acid substitutions in a few locations provide more heat-tolerant folds

• An increased number of ionic bonds between basic and acidic amino acids resist unfolding in the aqueous cytoplasm

• Production of solutes help stabilize proteins

Modifications in cytoplasmic membranes to ensure heat stability

• Bacteria have lipid rich in saturated fatty acids

  • Archaea have lipid monolayer rather than bilayer

To ensure heat stability bacteria have

lipids rich in saturated fatty acids

To ensure heat stability archaea have

lipid monolayer rather than bilayer

Neutrophiles

Evolved to grow best at low or high pH but most organisms grow best between pH 6 and 8

Acidophiles

Organisms that grow best at low pH (<6)

obligate acidophiles

membranes destroyed at neutral pH

Alkaliphiles

organisms that grow best at high pH (>9)

Nonhalophile

Growth rate decreases with addition of sodium chloride

Halotolerant

Growth rate is ok and can tolerate some addition of sodium chloride but has a pretty steady decline

Halophile

likes salt and can live with some, increasing concentrations decrease growth rate

Extreme halophile

Extreme percentages of salt increases growth rate until it plateaus

Obligate or strict aerobes

undergo aerobic respiration (no fermentation)

Obligate anaerobes

do not use aerobic metabolism

Facultative aerobes

can maintain life via fermentation or anaerobic respiration or by aerobic respiration

Microaerophiles

aerobes that require oxygen levels from 2 to 10% and have a limited ability to detoxify hydrogen peroxide and superoxide radicals (hydrogen peroxide can be converted w/catalase to H20 and O2)

Aerotolerant anaerobes

do not use aerobic metabolism but have some enzymes that detoxify oxygens poisonous forms

Superoxide

O2-

Hydrogen peroxide

H2O2

Hydroxyl radical

OH*

Water

H20

Catalase can destroy toxic oxygen species with what reaction

H2O2 + NADH + H+ → 2H2O + NAD+

Decontamination

The treatment of an object to make it safe to handle

Disinfection

Directly targets the removal of all pathogens, not necessarily all microorganisms. Generally uses disinfectants or antiseptics, but may use high heat

Disinfectants

Harsh chemicals that kill most microbes and are HARMFUL TO LIVING TISSUE

Antiseptics

milder chemicals USED ON SKIN or mucous membranes

Sterilization

the killing or removal of all viable organisms within a growth medium

Heat sterilization

the most widely used method of controlling microbial growth

decimal reduction time

the amount of time required to reduce viability tenfold (90% decrease from 100 to 10%)

Autoclave

a sealed device that uses steam under pressure

Functions of autoclave

• allows the temperature of water to get above 100 degrees celsius (usually water cannot because of vaporization unless pressure is added)

• Kills endospores

• It is not the pressure but the high temperature that kills the microbes

125 degrees celsius for 30 minutes is pretty standard

Pasteurization

uses heat to significantly reduce microbes in a liquid

How does pasteurization differ from sterilization

Pasteurization does not kill all organisms (uses enough heat to kill pathogens but compromise the liquid material)

Effects of radiation depend on what

wavelength, intensity, and duration

Ionizing radiation

ionizes water to form oxygen radicals, high degree of penetration, ex. XR, gamma rays, electron beams

Nonionizing radiation

does not form oxygen radicals, low penetration ex. UV

UV light/radiation forms what

a thymine dimer

Filtration removes what

microbes

What filter size do you need to remove microbes

0.45 or 0.2 or smaller

Germicidal agents

Biocidal agents and microbicidal agents are chemicals that kill microbes

Bactericidal agents

kill bacteria

fungicidal agents

kill fungi, including fungal spores

virucidal agents

destroy viruses

bacteriostatic agent

agents that specifically inhibits the metabolism and reproduction or stops growth of bacteria ex. fridge or freezer (fungistatic and virustatic agents accomplish the same with fungi and viruses)

Principles of effective disinfection

concentration of disinfectant (MIC)

Amount of organic matter

Time

Alcohol is a topical antiseptic, what is its mode of action

lipid solvent and protein denaturant

Phenol-containing compounds are used how

as soaps, lotions, cosmetics, deodorants, topical disinfectants; paper, leather, and textile industries

Phenol-containing compounds mode of action

disrupt cytoplasmic membrane

hydrogen peroxide mode of action

oxidizing agent

Hydrogen peroxide use

topical antiseptic

Iodophors (Betadine) mode of action

Iodinates proteins, rendering them nonfunctional; oxidizing agent

Octenidine mode of action

Cationic surfactant, disrupts cytoplasmic membrane

Types of disinfectants

phenols, phenolics, bisphenolics

Phenolics

ex. lysol

disrupt lipid containing plasma membranes and denature proteins

Bisphenolics

Ex. Hexachlorophene, triclosan, phisohex

Disrupt plasma membranes and denature proteins

Types of disinfectants

alcohols ex. Ethanol and Isopropanol

Denature proteins, disrupt membranes, dissolve lipids, work best in aqueous solutions, evaporate rapidly

Halogens

Intermediate-level antimicrobial chemicals (can kill most)

believed that they damage enzymes via oxidation or by denaturing them

most common is iodine

Oxidizing agents

Peroxides, ozone, and peracetic acid kill by oxidation of microbial enzymes

high-level disinfectants and antiseptics

Hydrogen peroxide can disinfect surfaces of objects

Catalase neutralizes; not useful for treating open wounds

Ozone is a treatment for drinking water

Peracetic acid; effective sporicide used to sterilize equipment

Heavy metals

Ions are antimicrobial because they alter the 3D shape of proteins, inhibiting or eliminating their function

Copper controls algal growth in reservoirs, fish tanks, swimming pools, and water storage tanks

Gaseous agents

Ethylene oxide is used in closed chambers to sterilize items

Denatures proteins and DNA by cross-linking functional groups

Used in hospitals and dental offices

Can be hazardous to people, often highly explosive, extremely poisonous, and potentially carcinogenic

Gene

functional unit of genetic information

genetic elements

genes, chromosomes, plasmids, transposons

Nucleic acids

contain genetic information via nucleotides (monomers of nucleic acids)

DNA and RNA are

polynucleotides

DNA is a

genetic blueprint

RNA is a

transcription product

Informational macromolecules

include nucleic acids and proteins (DNA, RNA, protein)

Central Dogma

DNA - RNA - Protein

Backbone of DNA chain is alternating

phosphates and the pentose sugar deoxyribose

Phosphate is connected where

5’ position

Phosphodiester bond is connected where

3’ position