An Introduction to Bacteria Flashcards
Cocci
Round bacteria. Diplo - pairs, strepto - chains, staphylo - clusters.
Bacilli
Rod shaped
Spirilla
Curve shaped to corkscrew like spiral
Pleomorphic
Can change shape
Factors affecting bacterial growth
Temperature, atmosphere, environment
Bacterial size
Very small so can only be seen under a microscope
Bacterial stains
Gram positive - purple, gram negative - pink/red
Bacterial structure
See diagram in notes page 11 book 1. Components; capsule, cytoplasmic/inner/plasma membrane, cell wall, cytoplasm, ribosomes, single chromosome - no nucleus, fimbriae, flagellum
Explain the differences between gram positive and gram negative bacteria
Gram positive bacteria has a plasma membrane, periplasmic space and peptidoglycan.
Gram negative bacteria has a plasma membrane, periplasmic space, peptidoglycan, space, outer membrane.
Cell surface
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.
Capsule function
Helps cell survive by preventing phagocytosis
Flagellum function
Motility. Monotrichous (one tail). Lopotrichous (one point). Amphitrichous (tail on both sides). Peritrichous (tails all over)
Fimbriae function
Adherence. Hair like structures
Spores
Formed by bacillus, clostridium and sporolactobacillus
Plasmids
Extrachromosomal, not found in all bacteria. They are small, circular, double-stranded DNA molecules which can conjugate bacteria with and without plasmids.
Bacteriophage
A virus that infects bacteria in a lysogenic cycle
Classification and nomenclature used for bacterial species
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.
Bacteria replication and genetic variation
Replication occurs through binary fission producing identical progeny. Variation occurs through spontaneous mutation and the transfer of DNA (transformation, transduction)
Detection and culture of bacteria
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.
