BACTERIA - Coggle Diagram
vibrio (one curve)
spirillum (two curves)
spirochete (more curves)
MICROBIOTA OF THE SKIN: dry environment, acidic pH because of sweat, high NaCl that causes osmotic lysis, inhibitory substances (lysozymes).
Staphylococcus Epidermidis: gram +, aerobe, halophilic, opportunistic pathogen (dismicrobism)
Propionibacterium Acne: gram +, anaerobe, prevents colonization by other microbes, can cause acne
follicle occlusion creates the perfect environment for the acterium, causes inflammation. Attraction of leukocytes causes the production of pus.
adhesiveness --> fimbriae, capsule. can be specific or non specific. Depends on tissue tropism, genetic specificity and on species specificity.
production of extracellular enzymes, such as hyaluronidase, collagenase, elastase, deoxyribonuclease, etc.
inhibition of phagocytosis and inhibition of fusion between the phagosome and the lysosome.
production of leukocytidin by pyogenic bacteria.
be surrounded by molecules that mimic host molecules.
coagulase, which makes the bacterium not accessible anymore.
protein A from S. Aureus: binds the constant chain of the antibody, neutralizing the antibody.
toxigenicity: ability to produce toxins
exotoxins: proteins, gram + and -, intracellular synthesis, thermolabile, immunogenic, non pyrogenic, form toxoids (--> vaccine).
antitetanic, anti diphteria ans anti pertussis vaccines
endotoxins: LPS, gram -, components of the soma, thermostable, resistant to gastric juices, non immunogenic, pyogenic, cannot form toxoid (no vaccines).
gram - bacteria have an external membrane, a periplasmic space, a thin dark layer of peptidoglycan. gram + bacteria have a thick peptidoglycan layer (90%):
PEPTIDOGLYCAN: polymer of glycan tetrapeptide, composed of two aminosugars (acetylglucosamine and acetylmuramic acid), they are connected by a beta 1-4 glycosidic bond. L-alanine, D-glutamic acid, D-alanine and Meso-diamino-pimelic acid. Opposite chains are interconnected:
in gram - the cross link occurs through the 3rd and the 4th aa of two chains;
in gram + the 3rd and 4th aa are connected by a bridge of 5 glycines.
the precursor is the glycan pentapeptide, which is linked to the opposite chain of peptidoglycan by transpeptidases, which remove the 5th aa and form a new link.
FLAGELLA and CILIA
flagella confer the ability to swim/swarm.
monotrichous (one flagellum at one end)
lophotricous (multiple flagella at one end)
amphitricous (single flagellum at two opposite ends)
peritrichous (flagella projecting in all directions)
sticky material produced by the bacterium and released. Not all bacteria have one.
MICROBIOTA OF THE ORAL CAVITY: ob served with the metagenomic approach (molecular amplification and sequencing of bacterial genes)
dental plaque: complex biofilm characterized by many bacteria with ecological succession.
primary colonization --> streptococci
secondary colonizers --> anaerobes
third colonizers --> gram - anaerobes.
Fusobacterium nucleatum binds all bacteria in the dental plaque (COAGGREGATION). Streptococci are cariogenic bacteria that can form cavities. They have dextransucrase, which catalyses the cleavage of saccarose into dextran and fructose.
in the STOMACH, only Helicobacter Pylori can survive. It is a curved gram - bacterium, causes chronic gastritis, ulceration, adenogastric carcinoma.
urease (ammonia and carbonic acid from urea --> able to neutralize locally the acidic pH of the stomach)
flagella (ability to swim)
some species can have the ability to initiate the sporulation cycle --> endospores are cells with a low metabolism and water content. ONLY CLOSTRIDIUM AND BACILLUS.
the risk of an opportunistic infection derives from:
in the INTESTINE, Clostridium Difficile is usually present and microbiota prevents the overgrowth. If the overgrowth occurs, PSEUDOMEMBRANOUS ENTEROCOLITIS.
in the VAGINA, there are many lactobacilli capable of metabolizing the high amounts og glycogen presen in the region in childbearing age.