Bacteria Flashcards
What shapes can bacteria be?
‣ Coccus (spheres) – strep: spheres in chains, staph: in clusters
‣ Bacillus (rods)
‣ Spirillum (spirals)
What colour is the staining of gram positive bacteria by crystal violet?
Stain BLUE by gram staining – large amounts of PEPTIDOGLYCAN (polysaccharide) in cell walls. Have no outer membrane.
What colour is gram negative bacteria when stained with cystal violet and why?
Stain PINK. Only thin layer of peptidoglycan in walls and have an outer membrane that prevents stain penetrating. Has outer membrane.
Define aerobic bactera
Bacteria that can survive in an oxygenated environment
Define facultative anaerobic organism
organism that can make ATP by aerobic respiration is O2 present but can switch to anaerobic
Define obligate aerobes
NEED oxygen to grow
Define antimicrobial
A substance which KILLS/INHIBITS bacterial growth. Synthetic molecules that interfere with microbial cell functions
Define antibotics
Also KILLS/INHIBITS bacterial growth. Agents are derived from a microorganism (blurred distinction between antimicrobial)
What is a disinfectant?
An antimicrobial applied to NON-LIVING MATERIAL to destroy microorganisms (Dettol spray)
Define antiseptic
An antimicrobial applied to NON-LIVING MATERIAL to destroy microorganisms (Dettol spray)
Define bactericidal
KILLS BACTERIA. (or viricidal/fungicidal)
Define bacteriostatic
INHIBITS BACTERIA. Antimicrobials can be bacteriostatic and bactericidal at diff levels
Define exogenous bacteria
Introduced to closed BIOLOGICAL SYSTEMS from external world via inhalation, consumption or cutaneous transmission. Exist in aquatic environments/atmosphere
aquatic (waterborne) Cholera ‣ Saprophytic (via soil) ‣ Zoonotic (food/drink)
Define endogenous bacteria
Endogenous bacteria – Naturally reside in a closed system (internal)
‣ e.g. E.coli of GIT enters urinary tract or normal flora of skin entering wound
Define virulence
Ability to cause disease (surface associated – flagella ,pili – or extracellular toxins)
What is commensalism?
bacterium benefits host and is neither harmed nor helped
‣ e.g. Staphlococcus/Micrococcus on human skin
What is symbiosis?
bacterium and host BOTH BENEFIT ‣ e.g. harmless oral bacteria preventing Candida albicans colonisation thus preventing a candida infection - thrush
What is parasitism?
‣ bacterium benefits, HOST IS HARMED ‣ e.g. Neisseria gonorrhoeae causing gonorrhoea
Describe streptococcus bacterium’s structure, class and role in disease
‣ Facultative anaerobic cocci. Produce energy via anaerobic glycolysis. Gram positive
‣ Occurs in chains or pairs
‣ Produce lactic acid. Like pH 5.5.
‣ S. mutans - the pioneer species associated with smooth surface caries and endocarditis. Appear after tooth eruption due to new hard surface habitats. Convert SUCROSE into glucose and fructose, or use other sugars to produce lactic acid.
‣ S. sanguis – can also colonise heart valves – bacterial endocarditis
‣ S. salivarius – soon colonise oral cavity of newborn
‣ Glycosyltransferases– an enzyme induced by streptococci. Convert sucrose into sticky polysaccharide fructose. Fructose and glucose are adhesives.
What type of respiration does actinomyces engage in?
What disease is this bacterium associated with?
Faculatative anaerobe
Root caries
What type of respiration does lactobacilli engage in?
What disease are they associated with?
Facultative anaerobic
Poduce lactic acid - dental caries
Is staphyloccus gram negative or positive?
What type of respiration does this organism engage in?
Positive
Facultative anaerobe
What gram negative bacteria are in the mouth and what diseases are they associated with?
• Porphyromonas
‣ P.gingivalis – subgingival. major periodontal pathogen ‣ SUBGINGIVAL BACTERIA ARE ANAEROBES, ASACCHAROLYTIC ARE PROTEOLYTIC – conditions suit them.
• Prevotella
‣ P.intermedia (prevotella intermedia) -> periodonatal disease/ abscess/gingivitis (acute necrotising)
• Actinobacillus
‣ A. ACTINOMYCETEMCOMITANS – AGGRESSIVE PERIODONTITIS ‣ Peptidases and proteinases promote sub-gingival assachrolytic species
• Veilonella
‣ Converts acidic products to less acidic (specifically lactate into weaker acids) ‣ Very common bacteria in mouth along with streptococci
