Micro Quiz 1 Review

What are microorganisms?

extremely diverse organisms, too small to be seen with the naked eye, and they inhabit every environment that supports life.

Microbes are not all harmful - 3 examples

Gut microbes can help digest food using enzymes humans may lack

Soil microbes can fix nitrogen into more biologically useful forms

Antibiotics can produce compounds that inhibit other microorganisms

Microbes can be beneficial, harmful, or neutral depending on

their identity, location, and interactions

Prokaryotes and eukaryotes both are cells and have ribosomes + independent metabolisms, but prokaryotes do not have

a membrane bound nucleus

Prokaryotes examples

bacteria and archaea

Eukaryote examples

Fungi, algae, protozoa

Viruses are not cells, they dont have

a membrane bound nucleus, ribosomes, or independent metabolism

example of a virus

bacteriophages

Viruses depend on

host cells to reproduce

Replication

DNA is copied

Transcription

DNA information is used to produce RNA

Translation

Ribosomes use mRNA to synthesize proteins

Enzymes

biological catalysts that accelerate chemical reactions

smaller cells have larger

surface-area-to-volume ratio

Larger surface-area-to-volume ratio is good for

faster exchange of nutrients across membrane

more efficient waste removal

supports rapid metabolism and growth

Resolution is the ability to

distinguish two closely spaced objects as separate

light microscopy resolves

many cells

electron microscopy can resolve

substantially smaller structures

staining increases

contrast, making cells easier o see

Gram staining sequence

crystal violet —> iodine —> alcohol —> Safranin

What is a Gram stain used for?

to classify bacterial species into two major groups (Gram + or Gram -)

Gram positive show as

purple b/c they retain the crystal violet

Gram negative show as

Pink b/c they take up the counterstain after decolorization

Gram-positive remain purple because

they have a thick peptidoglycan structure that traps the dye inside

Microbes grown in or on nutrient medium

culture

contains one type of microorganism

pure culture

prevents contamination

aseptic technique

encourages microorganisms with particular metabolic capabilities to grow

enrichment culture

many environmental microorganisms cannot be

readily cultured using standard laboratory methods

Louis Pasteur

Swan-neck flask experiment helped disprove spontaneous generation

Robert Koch

Established methods for linking specific microorganisms to infectious diseases

Carl Woese

compared rRNA sequences to investigate evolutionary relationships

Why did Carl Woese use rRNA?

Because all cells have ribosomes so all cells have rRNA

What are the three domains of life?

Bacteria, Eukarya, Archaea

If a microbe is unculturable

you collect an environmental sample, extract the DNA, copy rRNA genes, sequence them and compare

Whats a way to study an unculturable microbe in the lab?

Take the genes and clone it into a different microbe that is easy to study in the lab and see what new functions arise

The cell envelope refers to

all the structures surrounding the cytoplasm

5 structures in the cell envelope

cytoplasmic membrane, cell wall, outer membrane (in Gram -), periplasm, S layers

The cytoplasmic membrane is a phospholipid bilayer with

hydrophilic heads and hydrophobic tails

What are the 3 major functions of the cytoplasmic membrane?

1. selective permeability - controls what enters and leaves the cell

2. protein functions - contains proteins involved in transport, bioenergetics, and chemotaxis

3. energy conservation - maintains electrochemical gradient and proton motive force (PMF)

integral protein

embedded in the membrane

transmembrane protein

extends all the way across the membrane

peripheral membrane

loosely associated with the membrane surface

the proteins in the cell membrane can

transport nutrients, participate in energy generation, and detect environmental signals

Active transport move substances using

energy

What are the three types of active transport

simple transport, group translocation, ABC transport

simple transport

Uses energy of an existing electrochemical gradient, such as PMF to move substances

ABC transport

ATP-binding cassette transporters use ATP to drive transport (ATP binding protein, permease, substrate binding protein)

Group translocation

A substrate is chemically modified as it enters the cell

Symport

H+ and solute move in same directions

Antiport

H+ and solute move in different directions

The cell wall provides

rigidity, shape and protection against osmotic pressure

What is the major structural material in bacterial cell walls?

Peptidoglycan

Gram positive bacteria have

thick peptidoglycan layer, no outer membrane + purple

Gram negative bacteria have

thin petidoglycan, outer membrane and periplasm + pink

lysozyme

breaks down glycosidic bonds between peptidoglycan sugars

Penicillin

inhibits formation of peptidoglycan peptide cross-links

What two substances interfere with bacterial cell wall?

Penicillin + lysozyme

Archaea lack

peptidoglycan - so both lysozyme and penicillin won’t work

Lipopolysaccharide (LPS)

major component of Gram-negative outer membrane - surface recognition, virulence and structural properties

Porins

channel proteins in the outer membrane that allow certain small solutes to pass

Periplasm

The compartment between the cytoplasmic membrane and the outer membrane in Gram-negative bacteria. It has thin peptidoglycan layer and some proteins