Microbial Growth

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Microbial Growth Lecture 8

Image: Pearson Education Inc. (2004) publishing as Benjamin Cummings

Life and Metabolism • All living organisms obtain ___________(_________) from their environment. • Nutrients are needed as building materials for the cell and as a source of energy to do cellular work. • Nutrients are metabolized (broken down) into simpler molecules and _____________.

GlowingColonyEColi : A false-colored image from fluorescence microscopy of a growing colony of E coli cells. "Aging and Death in E. coli" (2005) PLoS Biol 3(2): e58 doi:10.1371/journal.pbio.0030058.

Microbial Growth • Refers to increase in the ____________ of microbes (reproduction) rather than an increase in ____ of the microbe. • Result of microbial growth is the ________ = aggregation of cells arising from single parent cell. • The time required for growth and reproduction is known as the doubling or ___________ ______. GlowingColonyEColi : A false-colored image from fluorescence microscopy of a growing colony of E coli cells. "Aging and Death in E. coli" (2005) PLoS Biol 3(2): e58 doi:10.1371/journal.pbio.0030058.

Growth of Microbial Populations

Image: Pearson Education Inc. (2004) publishing as Benjamin Cummings

___________________ in Cell Count From Binary Fission

Generation Number 0 1 2 3 4 5 10 20

Cell Count 1 2 4 8 16 32 1,024 1,048,576

View: http://www.cellsalive.com/qtmovs/ecoli_mov.htm Image: GlowingColonyEColi : A false-colored image from fluorescence microscopy of a growing colony of E coli cells. "Aging and Death in E. coli" (2005) PLoS Biol 3(2): e58 doi:10.1371/journal.pbio.0030058.

The Population Growth Curve

Image: Pearson Education Inc. (2004) publishing as Benjamin Cummings

Generation Time Under Optimal Conditions (at 37oC) Organism

Generation Time (min)

Bacillus cereus

28

Escherichia coli

12.5

Staphylococcus aureus (causes many infections: toxic shock syndrome one example)

27-30

Mycobacterium tuberculosis (agent of Tuberculosis)

Treponema pallidum (agent of Syphilis)

792 – 932

1,980

Mycolic Acid, Generation Time & Disease Meet the Microbe!

TB Culture

Phylum Actinobacteria, HIGH G+C “GRAM-POSITIVE” BACTERIA

_______________ Genus of rod-shaped, acid-fast bacteria. The presence of mycolic acid in the cell wall gives Mycobacteria many characteristics that defy medical treatment. They give the organism increased resistance to chemical damage and dehydration.

Acid-fast stain

The mycolic acid also allows the bacterium to grow inside macrophages, effectively hiding it from the host's immune system.

M. tuberculosis doubles population every 18-24 hours, while M. leprae doubles population about every 14 days. Extremely long generation time; contributes to the chronic nature of both diseases.

Images: TBCulture : http://phil.cdc.gov/ (image #4428) CDC/Dr. George Kubica. Wiki.

Man with

MycobacteriumTuberculosis : CDC Public Health Image Library, Leprosy Elizabeth White (PHIL #8433). Leprosy : Public Domain, Wiki

Factors Influencing Microbial Growth •

•

•

•

•

Nutritional requirements

Oxygen requirements

Temperature

pH

Osmotic Pressure

Staphylococcus: Janice Haney Car , CDC PHIL#10046 This 2005 scanning electron micrograph (SEM) depicted numerous clumps of methicillin-resistant Staphylococcus aureus bacteria, commonly referred to by the acronym, MRSA

Nutrition - General • Organisms use a variety of nutrients for their energy needs and to build organic molecules and cellular structures. • Most common nutrients – those containing necessary elements such as __________ (1/2 of the dry weight of a prokaryotic cell), oxygen, nitrogen, and hydrogen. • Microbes obtain nutrients from variety of sources.

SalmonellaTyphimuniumYellow : Rocky Mountain Labs NIAID_NIH

Nutrition – Carbon

Four Basic Groups of Organisms Organisms can be categorized based on energy source & carbon (organic molecule) source.

inorganic source Autotroph means organism can make its own food

organic molecules Heterotrophs break down materials that they obtain from other organisms Image: Pearson Education Inc. (2004) publishing as Benjamin Cummings

Nutrition - Other Chemical Requirements 1. ________________ 2. ________________ 3. ________________ 4. ________________ make up a total of 95% of the dry weight of a bacterial cell. • The other 5% is composed of Calcium, Copper, Iron, Magnesium, Manganese, Phosphorus and Iron. • Other elements that are needed are __trace elements__. • These elements are needed in extremely small amounts. • Most trace elements can be found dissolved in water.

Microbes & Oxygen • Obligate ____________ – Need oxygen to stay alive. Aerobic respiration = Use of O2 to break down food into useable energy.

• Obligate ____________ – Die in presence of oxygen. It is poisonous to them. Anaerobic respiration = break down food into useable energy without the use of O2.

• _____________ Anaerobes – Not strict aerobes or anaerobes. Many yeasts and enteric bacteria…Escherichia coli and Staphylococcus aureus.

• ________________ bacteria – Require oxygen levels lower that that found under normal atmospheric conditions (Helicobacter pilori – found in stomach).

O2

• ________________ Anaerobes – Don’t use oxygen, but are not killed by it. (Lactobacilli - This genus will make pickles from cucumbers and cheese from milk.)

List on the board for next slide.

Microbes & Oxygen

Aerobic and anaerobic bacteria can be identified by growing them in liquid culture: 1: Obligate aerobic bacteria gather at top of test tube to absorb maximal amount of oxygen. 2: Obligate anaerobic bacteria gather at bottom to avoid oxygen. 3: Facultative anaerobes gather mostly at the top, since aerobic respiration is most beneficial; but as lack of oxygen does not hurt them, they can be found all along the test tube. 4: Microaerophiles gather at upper part of test tube, not at top. Require O2, but at low concentration. 5: Aerotolerant bacteria are not affected by oxygen, and they are evenly spread along the test tube.

Using oxygen (1/2 O2) in metabolism creates toxic waste. Microbes that are able to use aerobic respiration produce enzymes to detoxify oxygen: Catalase: H2O2 ------- H20 and 02 Superoxide dismutase (SOD): oxygen radical ----- H20 and O2

Microbes that don’t make these enzymes cannot exist in the presence of oxygen.

Meet the Microbe! Campylobacter jejuni Gram negative, curved rod. Deltaprotobacteria. Close relative of Helicobacter. Microaerophilic bacterium. Campylobacter infections are ____________. Commonly found in animal feces. We catch this from animals, particularly chickens. Causes “food poisoning”. One of the most common causes of human gastroenteritis in the world. 2 – 4 million cases in US per year, peaking in summer months. Usually not lifethreatening. Resolves within 24 hours – one week. We now have issues with C. jejuni being antibiotic resistant because we put antibiotics in animal feed.

Microbes & Temperature _____________ Three-dimensional shape because of the temperature sensitive hydrogen bonds. These bonds will usually break at higher temperatures, and protein become __________. Denatured proteins lose function. ____________ Also temperature sensitive. Become brittle if temperature is too low. If temperature too high, lipids will be more liquid in form. Outside membrane cannot preserve the integrity of the cell and it will disintegrate. Images: Myoglobin: Thomas Splettstoesser Wiki PublicDomain Lipid Bylayer Cholesterol: cellbio.utmb.edu/cellbio/membrane_intro.htm

Effects of Temperature on Growth

40oF

77oF

Most of our plates are incubated at 37oC (98.6oF). Conversion C to F = 1.8xC + 32 http://www.sciencemadesimple.com/conversions.html Image: Pearson Education Inc. (2004) publishing as Benjamin Cummings

95oF

Categories of Microbes Based on Temperature Range

Image: Pearson Education Inc. (2004) publishing as Benjamin Cummings

Meet the Microbe! Psychrophilic ________: Chlamydomonas nivalis

Images: ChlamydomonasNivalis: Green algae psychrophile, www-es.s.chiba-u.ac.jp/.../snowalgae_ak.html WatermelonSnow: Will Beback, Wiki WatermelonSnowball: http://exviking.net/mflowers/small/Chlamydomonas_nivalis.htm WatermelonSnowFootprint : https:/.../seki/planyourvisit/wheretoeat.htm

Meet the Microbe!

Listeria monocytogenes

Gram positive, rod-shaped psychrophile.

L. monocytogenes is widely distributed; found in soil, water, animals, birds, insects. Responsible for listeriosis. Rarely pathogenic in healthy adults (mild flu-like symptoms).

Can be lethal in pregnant women, fetuses, newborns elderly and immune compromised, causing meningitis or bacterimia. Transmitted from environment (contaminated food an water) to human, except in the case of pregnant woman passing on to fetus. In vulnerable populations can have a case fatality rate of 25%. Facultative intracellular pathogen. Triggers its own phagocytosis. Lysteria are very hardy. Can grow in temperatures ranging from 39°F (the temperature of a refrigerator) to 99°F.

Extreme _______________ Grand Prismatic Spring, Yellowstone National Park

Thermophiles produce some of the bright colors (the orange colors) seen in hot springs.

How do they tolerate the high temperatures? • cell membranes don’t contain fatty acids • special enzymes fold their DNA into special heat-stable coils • enzymes themselves are heat stable with extra bonds between amino acids.

pH As with temperature, bacteria have minimum, optimum and maximum pH ranges.

Meet the Microbe!

Helicobacter pylori

__________________ • Protozoans and most bacteria have an optimum pH range of 6.5 to 7.5. • pH range of human organs and tissues.

________________

• Most fungi & some bacteria grow best in acid niches. • Obligate acidophiles have to live in an acidic environment. • Acid-tolerant Microbes will survive in an acid environment, but do not prefer that.

Images: HelicobacterPylori : Electron micrograph of H. pylori possessing multiple flagella. Yutaka Tsutsumi, M.D. Professor Department of Pathology Fujita Health University School of Medicine

• Gram-negative, microaerophilic, and acidophilic bacterium.

• Can thrive in the stomach and

upper small intestines and cause ulcers.

• However, many who are infected do not show any symptoms.

• Helicobacter spp. only known

microorganisms to thrive in highly acidic environment of stomach.

pH : _________ Meet the Microbe!

Vibrio cholerae (Cholera bacteria) will grow outside the body at a pH of 9.0.

• Gram negative, vibrio-shaped, alkilinophile in class Gammaproteobacteria. • In environment, prefers warm, salty alkaline water and many Vibrio species can multiply in shellfish. • Vibrio cholerae can thrive in fresh water.

Physical Effects of Water • Water is important reactant in many metabolic reactions.

• Most cells die in absence of water.

- Some have cell walls that retain water. What genus comes to mind? - Endospores and cysts can cease most metabolic activity for years.

What organisms make endospores? Which make cysts?

• Cell walls of bacteria prevent them from exploding in a hypotonic environment, but most bacteria are vulnerable in hypertonic environments.

Osmotic Pressure Many bacteria can be plasmolyzed by high concentrations of solutes. The water moves out of the bacterium and it dies of ‘hyperosmostic shock’ (desiccation). Photo: Journal of Bacteriology http://jb.asm.org/content/vol188/issue10/cover.shtml

Why can you keep honey on the cupboard for months, even years, without it spoiling?

Osmotic Pressure & Salt Environments Obligate ______________ • Must live in a niche of high salt content. • Can grow in an environment up to 30% salt. • If placed within a freshwater environment, they will burst and die.

____________ Halophiles • Can survive and tolerate high salt niches, but do not require them to living.

Image: Staphylococcus Epidermis: CDC Public Health Image Library, Segrid McAllister (PHIL #259)

Glycocalyx & Osmotic Pressure Some bacteria have an additional layer outside of the cell wall called the glycocalyx. One type of glycocalyx is called a ______________________ . • glycoproteins loosely associated with the cell wall. •

cause bacteria to adhere to solid surfaces and help prevent the cell from drying out

Meet the Microbe!

The slime layer of Staphylococcus epidermidis allows it to exist on the salty environment of the skin. Mannitol Salt STRUCTURE OF MICOBIAL CELLS

Do you want to make this class easier?

Do yourself a favor. Use the…

Virtual Microbiology Classroom (VMC) !

Remember, every class meeting adds pieces to the puzzle!

The VMC is full of resources to help you succeed, including: • • • •

practice test questions review questions study guides and learning objectives photos of bacterial colonies, stains, media and other lab-related material

You can access the VMC through Moodle, or by going to www.ScienceProfOnline.com