An Introduction to Bacteria

Question 1

Cocci

Answer 1

Round bacteria. Diplo - pairs, strepto - chains, staphylo - clusters.

Question 2

Bacilli

Answer 2

Rod shaped

Question 3

Spirilla

Answer 3

Curve shaped to corkscrew like spiral

Question 4

Pleomorphic

Answer 4

Can change shape

Question 5

Factors affecting bacterial growth

Answer 5

Temperature, atmosphere, environment

Question 6

Bacterial size

Answer 6

Very small so can only be seen under a microscope

Question 7

Bacterial stains

Answer 7

Gram positive - purple, gram negative - pink/red

Question 8

Bacterial structure

Answer 8

See diagram in notes page 11 book 1. Components; capsule, cytoplasmic/inner/plasma membrane, cell wall, cytoplasm, ribosomes, single chromosome - no nucleus, fimbriae, flagellum

Question 9

Explain the differences between gram positive and gram negative bacteria

Answer 9

Gram positive bacteria has a plasma membrane, periplasmic space and peptidoglycan.
Gram negative bacteria has a plasma membrane, periplasmic space, peptidoglycan, space, outer membrane.

Question 10

Cell surface

Answer 10

Contains a plasma/cytoplasmic membrane, penicillin binding proteins cross links (transpeptidases, carboxypeptidases, endopeptidases), peptidoglycan/murein which provide strength and shape consisting of carbohydrate monomers. Gram negative bacteria will also have lipopolysaccharides which elicit strong immune responses.

Question 11

Capsule function

Answer 11

Helps cell survive by preventing phagocytosis

Question 12

Flagellum function

Answer 12

Motility. Monotrichous (one tail). Lopotrichous (one point). Amphitrichous (tail on both sides). Peritrichous (tails all over)

Question 13

Fimbriae function

Answer 13

Adherence. Hair like structures

Question 14

Spores

Answer 14

Formed by bacillus, clostridium and sporolactobacillus

Question 15

Plasmids

Answer 15

Extrachromosomal, not found in all bacteria. They are small, circular, double-stranded DNA molecules which can conjugate bacteria with and without plasmids.

Question 16

Bacteriophage

Answer 16

A virus that infects bacteria in a lysogenic cycle

Question 17

Classification and nomenclature used for bacterial species

Answer 17

Names are based on genus and species eg staphylococcus (genus) aureus (spp.). Strains of a species have similar characteristics. DNA typing techniques are used to identify strains.

Question 18

Bacteria replication and genetic variation

Answer 18

Replication occurs through binary fission producing identical progeny. Variation occurs through spontaneous mutation and the transfer of DNA (transformation, transduction)

Question 19

Detection and culture of bacteria

Answer 19

Individual bacteria are only seen through a microscope with x1000 oil immersion lens. It can be stained with a gram stain or fluorescent dyes.
Colonies can be cultured on a medium (e.g. agar) and are seen by the eye.