Microbes Exam #4

Though some are extreme, most cells have similar physical and chemical requirements. Compare physical and chemical requirements in general.

Physical Requirements: water, temperature (can’t be too cold or too hot, but some archaea can survive in extreme environments), oxygen (aerobes require oxygen for cellular respiration, while anaerobes will die in the presence of the gas - facultative organisms can grow with or without oxygen), pH (most organisms have an optimal pH as well as pH range where growth will be hindered) salt, and radiation. Chemical Requirements for Metabolism: energy, enzymes, organic macromolecules (carbohydrates, proteins, lipids), inorganic molecules (water, vitamins, minerals)

For the physical requirements, how do we classify microbes based on Temperature?

Can be classified as psychrophiles, psychrotrophs, mesophiles, thermophiles, and hyperthermophiles. Psychrophiles are organisms that live at cold temperature ranges -8*C (18*F) and 20*C (68*F) and can be found on the ocean floor or in Antarctic and Arctic environments. Psychrotrophs are organisms that live at cold temperature ranges (4*C - 5*C/ 39*F - 41*F) and grow well in refrigerator temps. Mesophiles are organisms that live at ambient temperature ranges 10*C (50*F) and 45*C (113*F) and are found in aquatic and soil environments in temperate and tropical regions around the world; most human pathogens are mesophiles. Thermophiles are organisms that live at high temperature ranges 40*C (104*F) and higher and thrive in compost heaps, and hot springs. Hyperthermophiles are prokaryotic organisms that have an optimal growth temperature above 100*C (212*F) and even above 121*C (250*F) and are found in hot-water vents in the Pacific Ocean floor.

For the physical requirements, how do we classify microbes based on pH?

Can be classified as Neutrophiles, Acidophiles, Extreme Acidophiles, and Alkaliphiles. Neutrophiles are most common with a pH between 5-8. Acidophiles can survive in a lower pH (around 3). Extreme Acidophiles can survive at a lower pH. Alkaliphiles live in a higher pH (around 11)

For the physical requirements, how do we classify microbes based on Oxygen needs?

Can be classified as Aerobes, Anaerobes, and Facultative (anaerobes). Aerobes require oxygen for growth. Anaerobes may die in the presence of oxygen. Facultative (anaerobes) can adapt without oxygen - prefer oxygen.

For the physical requirements, how do we classify microbes based on Salt Tolerance?

Organisms can be classified as Halophiles, which can survive in salt concentration of 9-27%. Most organisms prefer 1% salt.

Can microbes grow outside of their optimal conditions?

Yes, but their growth rate is typically slower, less efficient, and sometimes unsustainable over long periods.

What types of organic macromolecules do all cells need?

proteins, nucleic acids, carbohydrates, and lipids

Which specific type of organic macromolecule is most used for cellular energy?

carbohydrates

How do enzymes and energy contribute to chemical requirements?

by enabling complex biochemical reactions to occur rapidly and in a controlled manner under mild cellular conditions. Enzymes act as catalysts to drastically speed up reactions by lowering the activation energy barrier, while energy (primarily ATP) drives unfavorable reactions that would not happen on their own.

What is Metabolism?

Sum of all biochemical processes on a living cell

What is Anabolism?

Building of molecules (biosynthesis)

What is Catabolism?

Breaking down molecules (digestion or hydrosis)

Explain the properties of Enzymes and why they are important in cellular reactions.

Enzymes are highly specific meaning enzymes that are used in one chemical reaction will not be used in another type of reaction. Enzymes are also reusable, meaning in catalyzing reaction the enzyme itself is not changed and can be used other identical reactions were a product or products are released. Enzymes are also only required in small amounts meaning they can used thousands of times to catalyze the same reaction and ensure a fast and efficient metabolic reaction occurs.

Compare the terms enzyme, substrate, enzyme-substrate complex, and active site.

Enzyme - a reuseable protein molecule that brings about a chemical reaction while itself remaining unchanged. Substrate - the substance upon which an enzyme acts. Enzyme-substrate Complex - a temporary molecular structure formed when a substrate binds to an enzyme’s active site. Active site - the region of an enzyme where the substrate binds.

How do cells use ATP?

Cells use ATP (adenosine triphosphate) as their primary energy currency, breaking it down into ADP and phosphate to power essential activities.

How is energy released?

Energy is released from ATP when “P” bond is broken. Energy is released when an enzyme breaks the high-energy bond connecting the terminal phosphate group to the rest of the molecule.

What is the main purpose and reaction (using glucose) of aerobic cellular respiration?

to convert stored chemical energy into usable cellular fuel, adenosine triphosphate (ATP), providing energy for life functions

Distinguish the 3 stages of aerobic cellular respiration?

Glycolysis, Citric Acid Cycle, and Electron Transport Chain

The Glycolysis stage begins and ends with what?

Begins with glucose C6H12O6 (6 carbons) and ends with 2 pyruvates (3 carbons each)

The Citric Acid Cycle stage begins and ends with what?

Begins with 2 pyruvate molecules (3 carbons each from previous step) that are converted to 2 acetyl - CoA (2 carbons each). Ends with all original carbons being broken down (4 C02), 2 ATP, many more NADH, also FADH2.

The Electron Transport Chain stage begins and ends with what?

Begins with the acceptance of electrons from reduced coenzymes NADH and FADH2. Ends with the transfer of these electrons to oxygen (the final electron acceptor), which then combines with hydrogen ions to form water H2O.

Do cells use other molecules besides glucose for cellular respiration?

Yes, cells can also use carbohydrates, lipids, and proteins.

How are aerobic respiration, anaerobic respiration, and fermentation alike?

They all function to produce cellular energy (ATP) from nutrients, initiated by glycolysis, and involve redox reactions (transfer of electrons). They are used by organisms to break down glucose and generate energy, often using NAD+ to move electrons, even when oxygen is absent.

How are aerobic respiration, anaerobic respiration, and fermentation different in regard to stages and outcomes?

Aerobic respiration uses oxygen and involves glycolysis, citric acid cycle, and electron transport chain yielding 36-38 ATP. Anaerobic respiration does not use oxygen but uses an electron transport chain with different inorganic acceptors. Fermentation is an anaerobic, partial degradation of glucose only involving glycolysis, yielding just two ATP.

Explain the importance of Fermentation?

Is a biological tool that transforms food through microorganisms (yeast/bacteria) to enhance preservation, taste, texture, and nutrition.

What are some products made via fermentation?

yogurt, cheese, sourdough, bread, vinegar, and alcoholic beverages

Explain the main purpose and reactions in photosynthesis.

Light (photons) captured in pigments to convert energy to ATP and NADPH (another electron carrier) - energy trapping reactions. CO2 gas is used with ATP and NADPH to produce carbohydrates (glucose) - carbon trapping reactions. Glucose can be stored as starch.

Why (and when) is it necessary to control microbes?

It is necessary to control microbes because some are pathogenic and can cause disease in humans and other animals. Some circumstances require combating the effects of some microbes including in food safety, vaccinations, public sanitation, agriculture, and lab settings.

Compare moist and dry heat.

Moist heat includes using boiling water, autoclave pressure, and pasteurization to sterilize certain edibles such as milk, juice, and ice cream. Dry heat sterilizes certain objects using an oven, direct flame, or incinerator.

How does an autoclave work?

An autoclave is an apparatus that increases steam pressure above atmospheric pressure, allowing the temperature of the steam to increase 100*C to 121*C (250*F).

What types of radiation kills cells?

UV light, X rays, Gamma Rays, Irradiation

How does drying and filtration work?

Drying - without water growth is unlikely, bacterial endospores can remain viable, lyophilization (freeze drying), osmosis (can drive water out of the cell), essentially removes water content by using salt or sugar on certain foods to deter microorganisms. Filtration - particles get trapped in small pores (pore size differs between bacteria and viruses), can filter liquid or air. Essentially microorganisms get trapped on the filter and do not remain in the liquid or air.

What do low temperatures do to bacterial growth?

Slows growth but doesn’t kill microbes, preserves food

Identify the general principles for effective disinfection.

Pre-clean the surface, Select the correct type of disinfectant, Adhere to “Contact Time,” Follow label instructions, Consider environmental factors, Ensure safety while using the product

Why is important to read the label while using a disinfectant?

The label will instruct you on certain safety precautions such as wearing gloves or eyeglasses while using the product, as well as illustrating what can or cannot be mixed with the product. The label can also tell you how long the disinfectant needs to remain on the surface for optimal use. The label can also tell you how to properly dispose of the substance.

Do we always want to use the strongest strength disinfectant as possible?

No, it is not recommended to always use the strongest strength disinfectant possible. Using a disinfectant that is stronger than necessary can be ineffective, dangerous to health, damaging to surfaces, and harmful to the environment.

How is Ethyl Alcohol used to control microbial growth.

(70%) denatures and dissolves lipids, can be both an antiseptic and disinfectant, also mechanical removal with wiping of surface.

How are Peroxides used to control microbial growth.

bubbling reduces dirt and debris, reactive form of oxygen, superoxide and radical (O2-) is toxic to microbes, no longer recommended for wounds (damages tissues).

How are Halogens used to control microbial growth.

react with proteins to kill, iodine, chlorine (10% bleach solution highly effective).

How are Heavy Metals used to control microbial growth.

silver nitrite, mercury (but toxic), copper sulfate.

How are Soaps and Detergents used to control microbial growth.

some simply help with degerming, others can dissolve the cell membrane, ammonium chloride (quats) (often in mouthwash and cleaners).

How are Phenols used to control microbial growth.

Lysol’s, triclosan destroys cell membranes, chlorhexidine

How are Aldehydes used to control microbial growth.

inactivates proteins and nucleic acids (DNA), formaldehyde and formalin for embalming

How are Ethylene Oxide (Gas) used to control microbial growth.

can used to sterilize paper, plastics, and other materials, can explosive, can kill endospores.

Describe the contributions of Joseph Lister.

Was a Scottish surgeon who noticed most of his patients were dying after amputation. He wondered if his tools were causing infections and he began to use a carbolic acid spray on wounds (antisepsis), and found that many more patients survived

What is Sterilization?

The removal of all life forms, including bacterial spores and viruses.

What is Disinfection?

Removal and killing of most life forms but not endospores on non-living surfaces.

What is Antisepsis?

Removal and killing of most life forms but not endospores on living surfaces.

What is Sanitization?

Lowers microbes to a “safe” level.

What is Degerming?

Physically removing microbes but not killing.

What was the early history of antibiotic discovery? (Who were the key players?)

Paul Erlich was able to kill bacteria that caused syphilis (arsenic based compound). Gerhard Domagk cured his own daughter of a bacterial infection with prontosil. Selman Waksman coined the term “antibiotic” with streptomycin. Alexander Fleming accidentally discovered penicillin.

Understand briefly how (and on what) penicillin works.

Penicillin is an antibiotic that kills bacteria by preventing them from building a functional cell wall, causing them to burst due to osmotic pressure. It specifically targets actively dividing, mainly gram-positive, bacteria by inhibiting the enzyme (transpeptidase) required to cross-link peptidoglycan, a key structural component of the cell wall. Mold creates a boundary in which staphylococcic was unable to grow soon killing the gram-positive bacteria.

What other types of antibiotics are there and how or what do they work on?

Cephalosporins - antibiotic that interferes with the synthesis of the gram-positive cell wall. Vancomycin - antibiotic that is only used in serious bacterial infections because of potential serious side effects and also works to inhibit cell wall growth of gram-positive bacteria. Broad-spectrum antibiotics - are effective against both gram-positive and gram-negative bacteria by inhibiting translation. Sulfonamides (Sulfa Drugs) - synthetic antibiotics that slow down growth by interfering with the materials needed for DNA replication and RNA transcription.

What are the challenges with antibiotic resistance today?

Rapid spread of “superbugs” due to misuse in humans and agriculture, lack of new drug development, and weak infection control in low-resource settings. Many individuals are dying from previously treatable diseases. Antibiotics may not work at all in the future.

How can people be educated on the challenges with antibiotic resistance?

By understanding why this is a problem and why overuse is driving the problem. Some steps individuals can take to combat this global crisis is to not request antibiotics when not necessary, do not stop taking antibiotics prematurely because you could spread the infection, do not save antibiotics for future use or share them as they may not combat the correct bacteria.