LECTURE 15 High GC GRAM POSITIVE BACTERIA · PDF fileHigh GC GRAM POSITIVE BACTERIA. HIGH G+C GRAM POSITIVES •Actinomycetes ... Spectinomycin M. tuberculosis, N. gonorrhea Neomycin

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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….


• 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


IN SUMMARY:

ACTINOMYCETES REPRODUCTION

Fig. 11.19

Fig 11.19. Conidia of Streptomyces


• 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


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


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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)


tubercules (a type of granuloma) – small, hardnodules formed when macrophagessurround and phagocytize M.tuberculosis


Fig. 23.18

Fig. 23.18.Inflammatoryresponse forming aTubercle. Note thelack of nuclei indead cells in centerof tubercle.



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.


Table 23.9


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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


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



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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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!


happy hair follicle


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

LECTURE 15 High GC GRAM POSITIVE BACTERIA · PDF fileHigh GC GRAM POSITIVE BACTERIA. HIGH G+C GRAM POSITIVES •Actinomycetes ... Spectinomycin M. tuberculosis, N. gonorrhea Neomycin

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