Micro Exam 3

Chemical Analysis of Microbial Cell

• 70% water

• Proteins

• 96% of cell is composed of 10 elements:

96% of cell is composed of 10 elements:

carbon

hydrogen

oxygen

nitrogen

phosphorus

sulfur

potassium

calcium

magnessium

iron

nutrition

process by which chemical substances (nutrients) are acquired from the environment and used for cellular activities

– influence of adaptation

essential nutrients

must be provided to an organism

macronutrients

required in large quantities; play principal roles in cell structure and metabolism

• proteins, carbohydrates

micronutrients or trace elements

required in small amounts; involved as enzyme cofactors and in maintenance of protein structure

• manganese, zinc, nickel, cobalt, molybdenum, copper

inorganic nutrients

atom or molecule that contains a combination of atoms other than carbon & hydrogen

– metals & their salts (magnesium sulfate, ferric nitrate, sodium phosphate), gases (oxygen, carbon dioxide) & water

organic nutrients

contain carbon & hydrogen atoms & are usually the products of living things

– methane (CH ), carbohydrates, lipids, proteins & nucleic acids

Potassium

essential to protein synthesis and membrane function

Sodium

important to some types of cell transport

Calcium

cell wall and endospore stabilizer

Magnesium

component of chlorophyll; membrane and ribosome stabilizer

Iron

component of proteins of cell respiration

Environmental factors fundamentally affect the function of metabolic

enzymes

Factors include:

– temperature

– oxygen requirements

– osmotic pressure

– pH

– electromagnetic radiation – barometric pressure

– ecological associations

Understanding microbial ecological niches =

ability to control microbial growth

3 cardinal temperatures

most single cell organisms are poikilothermic

Minimum temperature

lowest temperature that permits a microbe’s growth & metabolism

Maximum temperature

highest temperature that permits a microbe’s growth & metabolism

Optimum temperature

promotes the fastest rate of growth & metabolism

Psychrophiles

optimum from to °C

– range from -10 to 20 C

Psychotolerant

– optimum to °C

–range of 4 to 35°C (grow slowly in cold)

Mesophiles

optimum from to °C

–range of 10 to 45°C

–majority of human pathogens & normal flora

Thermophile

optimum 67 to 72 °C

–range from 45 to 80°C

–compost pile or hot water heater

Extreme thermophiles

range >70 °C

–hot springs & deep ocean vents

–CM highly saturated lipids

Archae

unique enzymes; ↑G+C%; no PG; saturated CM lipids

–ex) Taq polymerase in PCR

Food Preservation

Temperatures in this range destroy most microbes, although lower temperatures take more time.

Very slow bacterial growth.

Rapid growth of bacteria; some may produce toxins.

Many bacteria survive; some may grow. Refrigerator temperatures; may allow slow growth of spoilage bacteria, very few pathogens.

No significant growth below freezing.

pH

• pH is a measure of the hydrogen ion concentration of a solution

• defined as the degree of acidity or alkalinity of a solution (0 – 14 scale)

pH of pure water is

7 = neutral

The optimum pH range for most organisms is

pH 6 to 8 because acid & base can be:

The optimum pH range for most organisms is pH 6 to 8 because acid & base can be:

– damaging to proteins – especially enzymes

– damaging to CM & other parts of cell (even DNA)

The effects of pH

– related to the concentration of acid in the medium & the protection that bacterial cell walls sometimes provide

Changes in pH can lead to

– denaturing of enzymes & other proteins

– interference with pumping ions at the cell membran

Many bacteria produce large quantities of acids as they metabolize & grow

leads to high acid concentration = toxic environment

Acidophiles

grow at extreme acid pH (0 to 5.5)

– hot springs Archaea

– Euglena mutabilis and Thermoplasma

Alkalophiles

grow between pH 8.5 to 12

– Proteobacteria in Mono Lake (Ca) live at pH 12

Natronomonas pharaonis

grows optimally at pH 8.5 in 3.5M NaCl (soda lakes)

Proteus (neutrophile)

metabolizes acidic urea to colonize urinary system

fungi can grow at—— pH than bacteria

lower

Helicobacter pylori

• Gram (-) spirochete w/ high motility

• found in stomach ~ pH 2-2.5

• causes peptic ulcers, gastric & esophageal cancer

• Produces toxins that cause inflammation & damage

– symptoms made worse by ↑stress, environmental factors & diet

• not acid-tolerant

• protects itself from HCl acid by growing in protective mucus layers of stomach

• Breaks down urea in stomach & produces NH +

Helicobacter pylori

(ammonia) to neutralize the microenvironment

• Treated w/ antibiotics

Oxygen

As oxygen is utilized it is transformed into several toxic products:

Most cells have developed enzymes that neutralize these chemicals:

If a microbe is not capable of dealing with toxic oxygen (anerobic) it is forced to live in oxygen free habitats.

As oxygen is utilized it is transformed into several toxic products

singlet oxygen ( O2),superoxide ion (O2-), peroxide

(H2O2), and hydroxyl radicals (OH )

Most cells have developed enzymes that neutralize these chemicals:

superoxide dismutase, catalase

Aerobe

utilizes oxygen and can detoxify it

Obligate aerobe

cannot grow w/o oxygen

– fungi, protozoa, Micrococcus & Bacillus

Faculative anaerobe

utilizes oxygen but can also grow in its absence (catalase+)

– prefers O2 but can survive w/o it

Microaerophilic

requires only a small amount of oxygen (1%-15%)

– optimum growth at 5 O2

Anaerobe

does not utilize oxygen

Obligate anaerobes

lacks the enzymes to detoxify oxygen so cannot survive in an oxygen environment

Aerotolerant anaerobes

do no utilize oxygen but can survive and grow in its presence

– Lactobacillus

Osmotic Pressure

Water availability & its solute concentration causes microbes to exist under hypotonic or isotonic conditions

Halophiles

require a high concentration of salt (salt lakes or ponds)

– Halobacterium (optimum growth in 25% NaCl)

Osmotolerant

do not require high concentration of solute but can tolerate it when it occurs

– Staphylococcus aureus (0.1%-20% NaCl)

Water activity

(Aw) is a measure of water that is available for use by an organism

Aw is ↓ by adding ________ to a solution

solutes

Aw is ↓ by adding solutes to a solution

–  solute concentration of solution

–  osmotic pressure & ↓Aw (inversely related)

– Enzymes require an aqueous environment to function

– ↓Aw →↓enzyme function =↓metabolism & death of cell

The Aw of pure water is

~1.00

Most organisms require an Aw of—- to——for metabolic activity & growth

0.90

1.00

Most organisms require an Aw of 0.90 to 1.00 for metabolic activity & growth ex

– Staphylococcus aureus → can grow at ~0.85 Aw

• grows on our salty skin

– Fungi → can grow at ~0.70 Aw

Salts/sugars =

decrease Aw = used as food preservatives

Nonionizing radiation

can be used to decontaminate items

– Ultraviolet light, microwaves, infrared radiation

– endospores can survive large doses of non-ionizing radiation

– UV light can cause mutations in DNA (T-T dimers) & sometimes kill organisms

– Some organisms have enzyme systems to repair certain kinds of DNA damage (soil bacteria)

Ionizing radiation

can fully sterilize many items

– gamma rays, x-rays, electron beams

– generate ions that destroy DNA &

proteins