Microbio 4000 Exam 1 Key Concepts

Gotta Cram!

What does the field of Microbiology study?

The study of microscopic organisms like bacteria, (viruses), archaea, fungi and protozoa.

What are the prokaryotic groups of microbes?

Bacteria

• Single celled, cell walls made of peptidoglycan, some can be pathogens and some can be extremophiles

Archaea

• Single-celled, no known pathogens but some can be extremophiles

What are the eukaryotic groups of microbes?

Protozoa

• “Animal-like, single celled eukaryotes, NO CELL WALL, some can be parasitic or pathogenic

Algae

• Photosynthetic eukaryotes with cell walls, can be both single and multi cellular, can release toxins but are not a pathogen

Fungi

• cell walls, yeasts are singled celled while olds and mushrooms are multi- some are pathogens

Helminths

• Multicellular, macroscopic parasites, flat- or round- worms, microscopic during first stages

What were the important observations made by Hooke and Van Leeuwenhoek? (mid 1600s)

Hooke built the first compound microscope and coined the term cells

Van Leeuwenhoek observed smaller organisms and bacteria with a stronger single-lens microscope (father of microbio)

What is the germ theory of disease and what is the importance of Koch’s postulates? (Late 1700s -1850s)

The idea that specific diseases are caused by specific microscopic “germs”.

Koch’s postulates were a scientific method used to determine of a specific microorganism causes a specific disease in which he used pure cultures (single colonies of bacteria)

What is the significance of Jenner’s discovery? (1796)

He deliberately infected patients with a less lethal version of a disease to build immunity against the human smallpox.

What did Pasteur realize is important for successful vaccination? (1870s - 80s)Hu

He realized the the dosage of the exposure to the disease is important so that the patient can be protected from the disease without having severe symptoms

Why is human microbiota important?

It helps with digestion, helps develop immune system, makes growth factors, etc.

What are the three domains of life and who is responsible for this organization?

Bacteria, Archaea, Eukarya

• Carl Woese (1977)

What are some key differences between prokaryotes and eukaryotes?

Prokaryotes

• No nucleus or membrane bound organelles, have a nucleoid region to store their DNA

Eukaryotes

• complex, often multicellular with a nucleus and specialized membrane-bound organelles

What does a Gram-negative bacteria contain?

Stain reddish pink

Thin Cell Wall

• Few Peptidoglycan layers with lipoproteins attached

Periplasm

• between membranes

Outer-membrane

• lipopolysaccharides (LPS) - O polysaccharide (O Antigen) layer is useful for identification and pathogen interaction, Core Polysaccharide, Lipid A (endotoxin)

S-layer

• Extra protein layer in some species

What does a Gram-positive bacteria cell contain?

Stain purple

Thick Cell Wall

• Many peptidoglycan layers

Teichoic Acids

• Carbohydrate chains (-)

Lipoteichoic Acids

• also attach to cell membrane

Gram Staining

Step 4: Decolorization step

• Alcohol dehydrates the thick peptidoglycan layer (Gram +) into a dense mesh like barrier; Crystal violet is retained

Gram Positive: remain purple

Gram Negative: CV stain is removed and then counterstain Pink (because of the 2 membranes present, the color doesn’t stick)

What are some bacteria classes that don’t Gram Stain well and why?

Mycobacteria

• have a complex cell wall that makes them resistant to gram staining (phylogenetically related to gram positives)

Mycoplasma

• LACK a cell wall so no peptidoglycan or outer membrane, cell membrane only

What is the composition of other microbial cell walls (not bacteria)?

Archaea

• Pseudomurein (not peptidoglycan), S-layers, can’t gram stain

Algae

• polysaccharides, and unique diatoms

Fungi

• Polysaccharides (chitin) and glycoproteins

What are the different kinds of passive transport?

Moves nutrients with the concentration gradient (high → low)

Simple diffusion - direct transport through the phospholipid membrane (+ Osmosis)

Facilitated Diffusion - a protein channel or carrier is used

What are different kinds of active transport?

Moving against the concentration gradient (low → High)

Primary transport & ABC transporters

• use ATP hydrolysis

• ATP-Binding Cassette - use siderophores which are helper molecules for scavenging scarce mineral like iron from outside the cell

Coupled Transport

• Symport - both moving in or both moving out (same)

• Antiport - one moving in and moving out (opposite)

Group Translocation

• Uses energy from high energy organic compound in the cell to power transport; PEP here (not ATP)

• Transported molecule is modified (phosphorylated) Transporter transfers a phosphate to the molecule that is being imported.

What is bacterial secretion and what is it used for?

The secretion of proteins, DNA, and other large molecules is crucial. These systems allow bacteria to interact with their environment, compete with other bacteria, adhere to surfaces, and modulate host immune responses

• Eukaryotes typically move extracellular proteins through exocytosis

Where are ribosomes found and how they differ in prok. and euk. cells?

Ribosomes are used to synthesize proteins

• located in the cytoplasm and nucleoid edge

• In Eukaryotes they are larger while in prokaryotes they are smaller and could be found in the mitochondria

What is the nucleoid?

Where bacterial DNA is organized

• double-stranded helix, supercoiled, and organized by DNA binding proteins into chromosomes (circular) and plasmids (non-essential genes transferred in horizontal gene transfer)

What is the endosymbiotic theory?

Larger cell engulfed smaller bacterial cells and provided protection. the smaller cell provided a benefit too. Symbiotic relationship (organelles)

Evidence for Endosymbiosis

• mitochondria and chloroplasts resemble bacteria in shape and size, have bacterial-like genomes have a double membrane

What is the difference between Eukaryotic and bacterial flagella?

Bacterial flagella

• Made from flagellin protein, motility, spin like a propeller, powered by the proton motive force

Eukaryotic cells

• Made up of microtubules underneath the cell membrane, whip-like motion, ATP hydrolysis

What structures do all bacterial cells need?

Plasma membrane, cytoplasm, ribosomes, membrane transporters, chromosomes

What is an axial filament and which microbe group has this?

Bundles of Endoflagella located under the outer membrane/ sheath, in the periplasm. Provides motility through connective tissue

• Spirochetes (group of bacteria)

What types of environmental energy sources do microbes use?

Light (photo-), Organic sources (organo-), and Inorganic sources (litho-)

What is the difference between catabolism and anabolism?

Catabolism - breaks things down and releases energy in the end

Anabolism - build things up and energy is consumed overall.

These chemical reactions provide energy and create substances that sustain life.

What are 3 ways in which cells transfer energy to ATP?

Substrate-level - an intermediate in catabolism directly provides energy (and H3PO4) to ADP

Oxidative - Energy from the oxidation (breakdown) of nutrients is used to create a Proton Motive Force (PMF) which drives the ATP synthase (respiration)

Photophosphorylation - light energy used to create a PMF which drives ATP synthase (photosynthesis)

What are electron carriers and how are they used in metabolism?

They help the cell harvest or transfer energy in a controlled and stepwise manner.

• They transfer electron energy from catabolism to other pathways.

What are the inputs and outputs of the glycolysis pathway?

Input: 1 glucose and 2 ATP

Output: 4 ATP (Net 2 ATP by SLP), 2 NADH, 2 Pyruvate, and intermediates

What is the input and output of the Preparatory step?

Input: per 1 glucose… 2 Pyruvate

Output: 2 NADH, 2 CO2, 2 Acetyl-CoA,, and intermediates

What are in the inputs and outputs of the TCA (Krebs) Cycle?

Oxidation of Acetyl-CoA → CO2

Input: 2 Acetyl CoA (2 turns)

Output: 4 CO2, 6 NADH, 2 FADH2, 2 ATP (SLP)

In respiration (starting with glucose and ending with ATP); How is the energy transferred? How do electrons flow or where are they transferred?

The electron transport chain (system) is a series of redox reactions that occur within the oxidoreductase enzyme. They pass electrons from the stronger e- donor to the stronger e- acceptor.

What is the Proton Motive Force?

The energy from the ETC allows for complexes to move or pump protons (H+) across a membrane, generating a chemiosmotic gradient

Why are microbial ETCs so diverse?

• Since they have no mitochondria, it occurs across the cell membrane

• the number and arrangement of complexes vary

• Cytochrome C placement

• Terminal Complex - many organisms use Cytochrome C oxidase which gives final electrons to O2 but this can vary because not all microbes have O2 as their final electron acceptor

What is the theoretical yield of ATP during Respiration?

38 ATP

Anaerobic Respiration

Same process as respiration but different final e- acceptor.

• Less energy but enables substantial growth even without O2. and requires a specific final enzyme complex in the ETC to transfer the final electron.

Fermentation

The partial catabolism of glucose (or other carbon source) where electron energy is transferred to pyruvate. ATP is produced without oxygen or other ETC final electron acceptors.

• Goal: regenerate NAD+

• Pyruvate is the final electron acceptor

• Net: 2 ATP per glucose

What is the difference between Lactic Acid and Ethanol fermentation?

Lactic acid fermentation - pyruvate is reduced to lactic acid.

• Gram-positives in cheese, yogurt, pickles, and muscle cells when O2 is low

Alcohol Fermentation - 1.) Pyruvate is converted to Acetaldehyde and CO2 is released. 2.) Acetaldehyde is then reduced to ethanol.

• Brewing, winemaking, and baking (Saccharomyces - yeast)

What must have microbe have to use a particular Carbon source?

Enzymes - to break down something used in central catabolism

Transporter - to get the carbon source into the cell

How do (chemo)lithotrophs (rock eaters) harvest energy from their environment?

They harvest electron energy from inorganic sources using an electron transport chain/system.

• lithotrophs are also autotrophs, they use CO2 and carbon fixation to fulfill the cell’s carbon needs.

• The amount of energy harvest is relatively inefficient per food molecule

• The final electron acceptor may or may not be O2

• Usually found in very specific environments.

• Oxidizers

What microbes groups utilize oxygenic phototrophy?

Algae and Cyanobacteria

• Oxygenic (use H2O; release O2)

What microbe groups utilize anoxygenic?

Purple Bacteria and Green Bacteria

• Anoxygenic (Use H2, H2S, etc.; NO O2 release)

What are Chemosynthesis and photosynthesis and compare and contrast their processes

Chemosynthesis - use energy and CO2 to synthesize organic carbon compounds (sugar) (Chemo-lithotrophs that use mineral oxidation)

Photosynthesis - use carbon fixation (phototrophs use light absorption)

What are autotrophs and what is carbon fixation?

Autotrophs make their own sugar (carbon)

Carbon fixation converts carbon dioxide into organic compounds (carbon) through the Calvin cycle and rubisco enzyme.

• requires a lot of energy and is the reverse of central catabolism.