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LECTURE 15
High GCGRAM POSITIVE
BACTERIA
.
HIGH G+C GRAM POSITIVES
• Actinomycetes
• Corynebacteria
• Propionic acid bacteria
• Bifidobacteria
• Micrococci
ACTINOMYCETES:morphology &reproduction
Fig. 12.15. Growth of filamentousmicrobes (fungus or actinomycetes).
Growth is from the hyphal tip.
ACTINOMYCETES MORPHOLOGY
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An actinomycete colony growing on agar - note the subterranean and aerial hyphae….
ACTINOMYCETES MORPHOLOGY
• have filamentous growth, like fungi
• on substrate, grow on and in it
• thallus -- tissuelike mass, grown in culture
• mycelium -- tangled mass of hyphae, found
in nature
ACTINOMYCETES MORPHOLOGY
IN SUMMARY:
ACTINOMYCETES REPRODUCTION
Fig. 11.19
Fig 11.19. Conidia of Streptomyces
ACTINOMYCETES REPRODUCTION
• actinomycetes (and fungi) reproduce via
spores
• hyphal growth is followed by fragmentationand release of spores
• conidia – spores produced asexually on
aerial filaments called sporophores
• shape and arrangement of sporophoreshelp identification of actinomycete taxa
ACTINOMYCETES REPRODUCTION
IN SUMMARY:
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ACTINOMYCETES:ecology • predominantly soil bacteria
• good at degrading recalcitrant
compounds such as chitin & cellulose
• often active at higher pH (contrast tofungi who may dominate at lower pH)
• give soil the “earthy” smell
ACTINOMYCETES ECOLOGY
Genus Frankia –
--large genus that all form nodules on certainnon-legume trees
--fixes nitrogen from the air and converts into
forms useable by plant host
--involved in “tripartite” relationship with plantand mycorrhizal fungus.
e.g.
Myrica in the tropics (invasive in Hawaii)Alnus in temperate climates (early succesional)
Ceanothus in USA (including gardens)
ACTINOMYCETES ECOLOGY ACTINOMYCETES ECOLOGY
Frankia nodules on Ceanothus roots
ACTINOMYCETES:antibiotics
• most important genus is Streptomyces -over 500 described species!
• produce many important antibiotics, including
Streptomycin - originally from S. griseus.
ACTINOMYCETES ANTIBIOTICS
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Other antibiotics produced by Streptomyces spp:
Antibiotic: affects:Spectinomycin M. tuberculosis, N. gonorrheaNeomycin Broad spectrum, topicalTetracyclines Broad spectrum,Chlamydias, Rickettsias etc.Nystatin Fungi, esp. CandidaErythromycin Gram + Bacteria andLegionellaChloramphenicol Broad spectrum, typhoid fever
ACTINOMYCETES ANTIBIOTICS ACTINOMYCETES ANTIBIOTICS
Inability of a test organism to grow in the presence ofStreptomyces
suggests antibiotic production by the latter
Fig. 04.18
Fig. 4.18. Secondary metabolites are produced at the end of thegrowth phase and during stationary phase….
ACTINOMYCETES ANTIBIOTICS
TUBERCULOSIS:pathology & history
• tubercular decay found in spinalcolumns of Egyptian mummies(2400BCE)
• Hipocrates (460BCE) described“phthisis” as most common diseaseof his time
• in 19th century Europe 1/7 of alldeaths attributed to TB
• afflicted famous people such as:Eleanor Roosevelt, Chopin, Checkov,Kafka, Robert Louis Stevenson, theentire Bronte family
• began a 19th century literary genre:the “tragic lingering death byconsumption” trophe
TUBERCULOSIS PATHOLOGY &HISTORY
TUBERCULOSIS PATHOLOGY &HISTORY
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Contraction: inhaling bacteria frominfected person
Primary stage: bacteria isolated bygranuloma in lungs called atubercule
Secondary stage: bacteria fail to beisolated, lesions form in lungs(coughing up blood)
TUBERCULOSIS PATHOLOGY &HISTORY
tubercules (a type of granuloma) – small, hardnodules formed when macrophagessurround and phagocytize M.tuberculosis
TUBERCULOSIS PATHOLOGY &HISTORY
Fig. 23.18
Fig. 23.18.Inflammatoryresponse forming aTubercle. Note thelack of nuclei indead cells in centerof tubercle.
TUBERCULOSIS PATHOLOGY &HISTORY
TUBERCULOSIS PATHOLOGY &HISTORY
Before antibiotics, the only treatment wasrest (to avoid secondary stage)… lead to
many “Sanitaria” (Sanitariums) especiallyin mountainous regions with clean dry
air (e.g. Boulder Mapleton Center, near
Mt. Sanitas).
• Robert Koch (remember him?) wasthe first to isolate Mycobacteriumtuberculosis in 1882
• Streptomycin was the first effectiveantibiotic against TB (late 1940s) alittle too late for WW2.
TUBERCULOSIS PATHOLOGY &HISTORY
Table 23.9
TUBERCULOSIS PATHOLOGY &HISTORY
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TUBERCULOSIS:physiology
TUBERCULOSIS PHYSIOLOGY
• Mycobacteria all produce mycolic
acids (mycosides) - long-chain “fats” -very hydrophobic and wax-like
• “Slow growing” mycobacteria (such asM. tuberculosis are so hydrophobic
that nutrients can’t easily diffuse in
• Mycolic acid is covalently bound to
the peptidoglycan layer ofMycobacteria
TUBERCULOSIS PHYSIOLOGY TUBERCULOSIS PHYSIOLOGY
TUBERCULOSIS PHYSIOLOGY
You saw carbolfuchsinin the Dorner endosporestain!!
Acid-alcohol fast test binds to mycolic acid. Good stain for bacteria too waxy for gram stain
Fig. 23.17. M.tuberculosis insputum sample. Acid-fast stain is
diagnostic formycobacteria.
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Virulence in M. tuberculosis associated with
cord factor
• 2 long chain alcohol groups hooked togetherby a disaccharide (trehalose)
• Cause cultures in media to have characteristic“corded” look
• Cord factor is implicated as causing severeweight loss in TB patients
• Cord factor is also a virulence factor becauseit binds cells of M. tuberculosis together sothat they are further resistant to our immunesystem
TUBERCULOSIS PHYSIOLOGY TUBERCULOSIS PHYSIOLOGY
TUBERCULOSIS:the disease today • In U.S., about 10,000,000 infected
individuals, many showing fewsymptoms
•12,000 deaths in U.S. per year
• very common disease as part of AIDSand in the homeless population…..
TUBERCULOSIS: THE DISEASE TODAY
Fig. 23.16
TUBERCULOSIS: THE DISEASE TODAY TUBERCULOSIS: THE DISEASE TODAY
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many cases are multi-drug resistant
TUBERCULOSIS: THE DISEASE TODAY
Many patients start feeling better after a month of
antibiotic therapy and stop using antibiotics - whichleads to more drug resistant bacteria. Best solution is
DOTS = direct observation therapy
TUBERCULOSIS: THE DISEASE TODAY
TUBERCULOSIS: THE DISEASE TODAY
CORYNEFORM BACTERIA
CORYNEFORM BACTERIA
• name comes from “club”: some areclub shaped
• are usually rod shaped (though staytuned) and arranged as Vs due tosnapping division
snapping division
• 2 thick peptidoglycan layers
• inner layer of cell wall grows inward to
divide 2 new cells. As it thickens, it putstension on outer wall until it ruptures. The
snapping tears the outer wall apart exceptat one point which holds the 2 cells
together like a hinge.
CORYNEFORM BACTERIA
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Fig. 11.14. Gram stain of a Corynebacterium -note V shapes
Some important genera of Coryneforms:
Arthrobacter spp. common soil inhabitants
rods when well fed and coccoid cells whenhungry. The coccoid cells are long-lived spore-
like cells.
Corynebacterium spp. are common aerobicorganisms of soil. One species, C. diphtheriaecauses diphtheria.
CORYNEFORM BACTERIA
Arthrobacter has a rod-coccus growth cycle
In log phase, they are rods that replicate viasnapping division. In stationary phase, they
are coccoid.
CORYNEFORM BACTERIA
diptheria
• Corynebacterium diptheriae usuallyspread by inhalation
• actual invasibility of the bacteria isminimal
• Produces powerful exotoxin thatdamages organs and causes build upof dead tissue in throat
• Exotoxin only produces if bacteriaare infected with a certainbacteriophage (virus) and iron levelsto be low
• 1 of 10 diptheria patients die
CORYNEFORM BACTERIA
PROPIONIC ACID BACTERIASwiss cheese:
•other bacteria (e.g. lactobacilli) fermentmilk’s lactose to lactic acid, form curds
•Propionibacteria then multiply, producing
acetate, CO2 & propionic acid
PROPIONIC ACID BACTERIA
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PROPIONIC ACID BACTERIA
Fig. 06.23
Fig. 6.23
PROPIONIC ACIDBACTERIA
Propionibacteria acnes in skin:
• anaerobic bacteria found in hair follicles(densities up to 107 per square cm of skin)
• growth enhanced by secretions ofsebaceous glands
• under normal conditions, P. acnes isbeneficial: creates low pH skinenvironment hostile to pathogens
• when sebaceous gland gets clogged, P.acnes multiplies in trapped sebum: ACNE!
PROPIONIC ACID BACTERIA
happy hair follicle
PROPIONIC ACID BACTERIA
BIFIDOBACTERIUM Bifidobacterium bifidus• anaerobic
• ferments a specific amino sugar and
lactulose (a disaccharide consisting offructose and galactose) found in breast
milk
• breast milk also contains bifidus factor, anoligosaccharide that specifically promotes
bifidus colonization
• one of the initial colonists of the intestinesof human babies
• also added to yogurt….
BIFIDOBACTERIUM
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Fig. 11.12MICROCOCCUS
MICROCOCCUS
•oligate aerobic cocci
•Have high %GC but morphologically dissimilarto the rest of the high GC gram + bacteria
•usually yellow, orange, or red in color
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