Lecture 1: Microbiology: An introduction

Question 1

Define the term microorganism

Answer 1

a very small living organism that can only be seen through a microscope

Question 2

What is microbiology

Answer 2

the study of very small living organisms

Question 3

How are microorganisms classfied?

Answer 3

1. bacteria
2. archaeans
3. protozoa
4. molds and yeasts
5. viruses

Question 4

Give some examples of microorganisms that can live under extreme conditions

Answer 4

halophiles - need high salt conditions
thermophiles - can thrive at high temperatures (60°-120°)
cryophiles - grow at cold temps (15° and lower)
acidophile, alkaliphile, xerophile (dry conditions)

Question 5

light microscopy can go up to what mangification scale

Answer 5

1000x

Question 6

List the key differences between prokaryotes and eukaryotes

Answer 6

prokaryotes - small, bacteria, haploid, no membrane around nucleus, circular DNA, asexual reproduction by binary fission, simple flagellum, resiprate via cytoplasmic membrane no ER, free ribosomes, cell wall is peptidoglycan

eukaryotes - large, protozoa, algae, fungi, animals and plants, diploid, membrane bound nucleus, strands of DNA, sexual and asexual reproduction, complex flagellum, respirate via mitochondira, complex organelles, cell wall made of chitin (fungi) and pectin (plants)

Question 7

Name the six different types of microscopes and their functions

Answer 7

1. brightfield - gram staining
2. darkfield - thin organisms with dark background
3. phase contrast - unstained organisms
4. fluorescence - immunodiagnostic tool
5. SEM - surface 3D
6. TEM - organelles, internal structures

Question 8

List the Biological Hierarchical classification

Answer 8

Species, Genus, Family, Order, Class, Phylum, Kingdom, Domain, Life

Question 9

Define strain

Answer 9

genetic variant of a species (subtype)

Question 10

define serotype

Answer 10

subtype (strain) that can be defines using specific antibodies from the serum in blood

Question 11

define pathovar

Answer 11

subtype with tissue/host specificity

Question 12

define isolate

Answer 12

pure micorbial sample obtained from infected indivdual

Question 13

How do bacteria grow/cell division

Answer 13

binary fission; haploid genome, duplication of chroosme, continues cell growth, division into two cells

Question 14

explain bacterial growth kinetics

Answer 14

lag phase - bacteria getting used to new environemnt, expressing enzymes (“setting the table for dinner”)
growth phase - eating up the nutriens, growing, multiplying
stationary phase - become dormant, no more food
death phase - bacteria start to die off

Question 15

What is a coccus

Answer 15

round shaped bacteria

Question 16

what is a bacillus

Answer 16

rod shaped bacteria

Question 17

what is a vibrio

Answer 17

curved shaped bacteria

Question 18

what is a coccobacillus

Answer 18

egg shapes bacteria

Question 19

What is a fusiform bacillus

Answer 19

long oval shaped bacteria

Question 20

Describe the different arrangements of bacteria

Answer 20

staphylo - triangular
strepto - chain
diplo - two
tetrad - four

Question 21

What is the morphological difference between Gram positive and Gram negative bacteria

Answer 21

gram positive - thick peptidoglycan wall, crosslinked by peptides, only has cytoplasmic membrane

gram negative - thin peptidoglycan layer, has an outer membrane

Question 22

What are the external morphological structures of bacteria

Answer 22

1. flagella
2. fimbriae/pilus
3. slime layers and capsule

Question 23

How do flagella move?

Answer 23

powered by a proton motive force in a whip like motion

Question 24

What is the structure and function of fibriae (pili)

Answer 24

structure - rigid, adhesin attached to pilus to attach to host cell, no motility

function - pili used for DNA transfer –> conjugation

Question 25

What is the structure and function of the slime layer of bacteria

Answer 25

structure - not organised, bacteria loosely attached

function - gliding, aggregation - sticks to surface and bacteria sticks with it, colonisation of smooth surfaces

eg. plaque on teeth

Question 26

What is the structure and function of the capsule

Answer 26

structure - highly organised, bacteria found inside capsule, rigid, bacteria firmly attached

function - bacterial adhesion to surfaces, acts as a defense mechanism against host immunity

Question 27

what are endospores

Answer 27

resistant to heat, cold, drying and many chemmicals - hard to get rid of them, survive many years