Microbial Products · Vitamin B1 (Thiamine) Vitamin B6 (pyridoxol) Folic acid Ergosterol (vitamin...
Transcript of Microbial Products · Vitamin B1 (Thiamine) Vitamin B6 (pyridoxol) Folic acid Ergosterol (vitamin...
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A. Primary Metabolites: log phase, use nutrients fast, produce PM
B. Secondary Metabolites: depletion of nutrients, growth retards, produce SM
Microbial Products
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Primary Metabolites: Vitamins
Vitamins: cannot be synthesized by higher organismsBut microorganisms are capable of synthesizing (gut)
ThiamineRiboflavinPyridoxineFolic acidPantothenic acidBiotinVitamin B12Ascorbic acidb- carotene (provitamin A)Ergosterol (vitamin D)
Studies reveal vitamin deficiencies Reported beneficial health effects Growing vitamin market demand (cost
effective) Genetically engineered MO as alternatives to
chemical synthesis
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Vitamins
Fat soluble Water soluble
Carotenoidsb-carotene (provitamin A)Astaxanthin
Poly unsaturated Fatty acids (PUFA; vitamin F)Docosahexaenoic acid (DHA)Arachidonic acid (ARA)
Riboflavin (vitamin B2)Cobalamin (vitamin B12)L-Ascorbic acid (Vitamin C)
R-Pantothenic acid (vitamin B5)D-Biotin (vitamin H or B7)Vitamin B1 (Thiamine)Vitamin B6 (pyridoxol)Folic acid
Ergosterol (vitamin D)
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Vitamin B12 or Cyanocobalamin
• Water soluble vitamin ; complex sructure• Has role in functioning of brain and nervous system, formation of
blood• Contains rare element cobalt
• Deficiency causes pernicious anemia which is an causes low Hb, lessRBCs
• Pernicious anemia: autoimmune disorder, parietal cells (stomach)responsible for secreting intrinsic factor are destroyed. Intrinsicfactor is crucial for the normal absorption of B12, so a lack ofintrinsic factor, as seen in pernicious anemia, causes a deficiency ofVitamin B12
• dietary reference intake for an adult ranges from 2 to 3 µg per day• used in treating cyanide poisoning, prevents brain atrophy in
Alzheimer’s patients
• COMMON INGREDIENT IN ENERGY DRINKS
http://en.wikipedia.org/wiki/Dietary_reference_intake
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cobinamide
nucleotide
• Corrin ring• Deep red colour due to corrin
ring • Central Co atom• Coordination state 6• 4 of 6 coord sites have pyrrole
ring• 5 has dimethylbenzimidazole
group• 6 is center of reactivity,
variab;e• CN, OH, Me, 5-deoxyadenosyl
for 4 types of B12
4 Pyrrole unitsPyrrole nitrogen
5,6-dimethyl benzimindazole
C63 H88 CoN14 O14P
12
34
5
6
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Commercial production
Genera known to produce vit B12
Most commonly used for industrial production are Streptomyces griesusPseudomonas denitrificans (aerobic)Salmonella typhimuriu (anaerobic)Propionibacterium shermanii GRAS by FDA
(anaerobic) (Generally Regarded As Safe)
Sanofi-Aventis (FRENCH) use genetically engineered versions to produce vitB12 under specialized conditions from Propionibacterium since they have no endotoxins or exotoxins
P. denitrificans also used after strain modification; mutant more efficient than wild type
20mg/L
Chemical syn not feasible
http://en.wikipedia.org/wiki/Acetobacteriumhttp://en.wikipedia.org/wiki/Aerobacterhttp://en.wikipedia.org/wiki/Agrobacteriumhttp://en.wikipedia.org/wiki/Alcaligeneshttp://en.wikipedia.org/wiki/Azotobacterhttp://en.wikipedia.org/wiki/Bacillushttp://en.wikipedia.org/wiki/Clostridiumhttp://en.wikipedia.org/wiki/Corynebacteriumhttp://en.wikipedia.org/wiki/Flavobacteriumhttp://en.wikipedia.org/wiki/Micromonosporahttp://en.wikipedia.org/wiki/Mycobacteriumhttp://en.wikipedia.org/wiki/Nocardiahttp://en.wikipedia.org/wiki/Propionibacteriumhttp://en.wikipedia.org/w/index.php?title=Protaminobacter&action=edit&redlink=1http://en.wikipedia.org/wiki/Proteus_(bacterium)http://en.wikipedia.org/wiki/Pseudomonashttp://en.wikipedia.org/wiki/Rhizobiumhttp://en.wikipedia.org/wiki/Salmonellahttp://en.wikipedia.org/wiki/Serratiahttp://en.wikipedia.org/wiki/Streptomyceshttp://en.wikipedia.org/wiki/Streptococcushttp://en.wikipedia.org/wiki/Xanthomonas
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Commercial production
• Produced in continuous culture with 2 fermenters in series
Anaerobic70h
Aerobic 50h
GlucoseCorn steep Betaine (5%)Cobalt (5ppm)pH 7.5 +
Propionibacteriumfreudenreichii
Cobinamide production and accumulation
Nucleotide synthesizedCombined with cobinamideTo yield 2ppm of cobalamin
Acidification of cultureTo 2-3pH/ 100oCFilter to remove cell debris
Filtrate
KCN added
CYNACOBALAMIN80% purityUsed as feed additive
Addition of 5,6-dimethylbenzimidazol (0.1%)
Betaine: sugar beet molasses
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Commercial production
ANAEROBIC PHASE
2-4 DAYS5-deoxyadenosylcobinamide produced
AEROBIC PHASE
5,6-dimethylbenzimidazole isadded and gets incorporated toform 5’-deoxyadenosylcobalamin
During the 7-day fermentation run, adenosylcobalamin is predominantlysecreted from the biomass and accumulates in the fermentation broth inmilligram amounts.
The down- stream steps comprise filtration, cyanide treatment,chromatography, extraction, and crystallization yielding vitamin B12 inhigh purity.
If to be used for treatment further purification (95-98% Purity)
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Commercial production
Pseudomonas denitrificans: strain improvements resulted in increase in yeildFrom 0.6mg/L to 60mg/L
Glucose : common carbon
Alcohols (methanol, ethanol, isopropanol)Hydrocarbons(alkanes, decane, hexadecane)
With methanol 42mg/L was obtained using Methanosarcina barkeri
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Riboflavin (Rf) or Vitamin B2
• Water soluble• Essential for growth and reproduction; key role in energy metabolism, ketone bodies,
fats, CHO and protein metabolism• Deficiency leads to cheliosis (fissures around mouth), glossitis (purple tounge) and
dermatitis• Required in coenzymes FAD (flavin adenine dinucleotide) and FMN (flavin
mononucleotide)• Used as an orange-red food colour additive, designated in Europe as E101
7,8-dimethyl-10- (D-19-ribityl) isoalloxazine
Participates in O-R reactions
Flavin is ring moiety with yellow colour to oxidized form
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FADE101
FMNE101a
Isoalloxazine ring Isoalloxazine ring
Ribitol
H
H
genes encoding the riboflavin biosynthetic enzymes are well conserved among bacteria and fungi
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Processed food is often fortified by the use of riboflavin as a colorant or vitaminsupplement.
The main application (70%) of commercial riboflavin is in animal feed, since productivelivestock, especially poultry and pigs, show growth retardation and diarrhea in case ofriboflavin deficiency.
According to a report by SRIC, a consulting company in Menlo Park (California), in 2005the need for industrially produced riboflavin was estimated at 6500–7000 tons peryear.
INDUSTRIAL USE
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Commercial production
Glucose
50% by biotransformationusing Bacillus pumulis
D-ribose
20% production by Chemical synthesis
Riboflavin
1/3rd production by direct fermentation
Acetone butanol fermentationClostridium acetobutylicumC. butylicum riboflavin as
by product
Ashbya gossypiiCandida famataBacillus subtillis (genetically modified)
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Major riboflavin producers are DSM Nutritional Products(Switzerland) and Hubei Guangji (Hubei Province, China), both usinggenetically engineered B. subtilis production strains, and BASF (first inGermany but now in South Korea), employing genetically engineered A.gossypii.
Commercial production
Phase I use of glucose, accumulation of pyr, pH acidic, growth stops, no Riboflv
Phase II decr pyr, incr in ammonia, alkalinity incr, prod of Riboflv in form of FAD and FMN
Phase III autolysis, cell disruption, release of free FAD, FMN and riboflv
Carbon sources: glucose, acetate, methanol, aliphatic hydrocarbons
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Ascorbic acid or Vitamin C
Precursor for its chemical synthesis can be obtained by biological methods
• Used in collagen biosynthesis, protects against nitrosamines, free radicals• Deficiency causes scurvy
feed applications of L-ascorbic acid account for only 10%, whereas the mainuses are in thepharmaceutical industry (50%),food (25%), andbeverages (15%).Pharmaceutical applications include stimulation of collagen synthesis(especially cosmetic products) and high antioxidant capacity, used for thereported health benefits in the prevention of flu, heart diseases, and cancer,as well as an antidote for poisoning.The food and beverage industry predominantly exploits the antioxidantcapacity of L-ascorbic acid to extend durability, prevent discoloration,and to protect flavor and nutrient contents of their products.
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D-glucose (200g)
Submerged bioreactor fermentation
D-sorbitol
sorbitol dehydrogenase
L-Sorbosechemical oxidation
2 keto L gulonic acid
Enol form of 2 keto L gulonic acid
acid treatment
L-ASCORBIC ACID (100g)
Acetobacter xylinum, A,suboxydans
Glucuronic acid
Gluconolactone
L-Gluconolactone
L-ASCORBIC ACID
L-Gluconolactonedehydrogenase
Reichstein Grussner synthesis
Erwinia sp.Acetobacter sp.Gluconobacter sp.
2,5-diketogluconic acid
2-keto L-gluconic acid
L-ASCORBIC ACID
Corynebacterium sp.
2,5-diketogluconic acidreductase
2,5-diketogluconic acidReductase of Corynebacterium into Erwinia herbicola
Cloning of gene
Bacillus megaterium
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b- carotene or provitamin A
Provitamin A -----> Vitamin A (intestine)
• Fat soluble• Deficiency leads to night blindness• Best source is liver and whole milk also coloured fruits and vegetables
• Isoprene derivatives• Tetraterpenoids with eight isoprene residues• 400 naturally occurring carotenoids: b-carotene, a-carotene, d-carotene, lycopene,
zeaxanthin
Carotenoids Used as food colorants and animal feed supplements for poultryand aquaculture, carotenoids play an increasing role in cosmetic andpharmaceutical applications due to their antioxidant properties.
The pigments are often regarded as the driving force of the nutraceuticalboom, since they not only exhibit significant anticarcinogenic activities but alsopromote ocular health, can improve immune response, and prevent chronicdegenerative diseases.
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Commercial production Microbial fermentationBlakeslea trispora (high yeild; 7g/L)Phycomyces blakesleeanusChoanephora cucurbitarumSubmerged Fermentation process
Corn starch, soyabean meal, b-ionone, antioxidants
DSM Nutritional Products (Switzerland) and BASF (Germany)dominate the market with their chemical synthesis processes,but Chinese competitors are catching up.
Trisporic acid: act as microbial sex hormone, improves yieldb-Ionone: incr b-carotene syn by incr enzyme activityPurified deodorized kerosene increases solubility of hydrophobic substrates
Recovery: b- carotene rich mycelium used as feed additiveMycelium is dehydrated by methanol, extracted in methylene chlorideand crystallized which is 70-85% pure
stimulators
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Halophilic green microalgae Dunaliella salina. It accumulates the pigments in oilglo- bules in the chloroplast interthylakoid spaces, protecting them againstphotoinhibition and photodestruction.
Excessive pigment formation in D. salina is achieved by numerous stress factorslike high temperature, lack of nitrogen and phosphate but excess of carbon, highlight intensity, and high salt concentration, the latter two having the highestimpact.
Dried D. salina biomass for sale contains 10–16% carotenoids, mainly b-carotene.In addition crystalline material obtained after extraction with edible oil is alsosold.
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Primary Metabolites: Organic Acids
Organic acids are produced by through metabolisms of carbohydrates. They accumulate inthe broth of the fermenter from where they are separated and purified.
GlycolysisKrebs cycle
I. Terminal end products lactic acid(pyruvate, alcohol) Propionic acid
II. Incomplete oxidation of sugars citric acid(glucose) Itaconic acid
Gluconic acid
III. Dehydrogenation of alcohol with O2 acetic acid
Manufactured on large scale as pure products or as salts
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CITRIC ACID: industrial uses
Flavoring agentIn food and beverages
Jams, candies, deserts,frozen fruits, softdrinks, wine
Antioxidants andpreservative
Chemical industryAntifoamTreatment of textilesMetal industry, puremetals +citrate (chelatingagent)
Pharmaceutical industryTrisodium citrate (blood preservative)Preservation of ointments and cosmeticsSource of iron
Agent for stabilization of Fats, oil or ascorbic acidStabilizer for cheese preparation
Detergent cleaning industryReplace polyphosphates
AcidifyerFlavoringChelating agentPrimary metabolitePresent in all organisms
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Aspergillus nigerA. clavatusPencillium luteum
Commercial Production
Strains that can tolerate high sugar and low pH with reduced synthesis of undesirable by products (oxalic acid, isocitric acid,
gluconic acid)
Glucose
Pyruvate
Pyruvate
Acetyl CoA
CO2
CO2
Pyruvate
OXA
Malate
MITOCHONDRIA
Malate Fumarate Succinyl CoA
OXA
citric acida-KG
CYTOPLASM
Glucose MEDIUM
Pyr carboxylase
Pyr Dehy-drogenase
Citratesynthase
100g sucrose --- 112g any citric acid or 123g citric acid-1hydrate
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Factors for regulation
CARBOHYDRATE SOURCE: sugar should be 12-25% Molasses (sugar cane or sugar beet) Starch (potato) Date syrup Cotton waste Banana extract Sweet potato pulp Brewery waste Pineapple waste
High sugar conc incr uptake and production of citric acid
TRACE METALS: Mn2+, Fe3+, Zn2+ incr yield Mn2+ incr glycolysis Fe3+ is a cofator for enzymes like aconitase
pH: incr yield when pH below 2.5, production of oxalic acid and gluconic acid is suppressed and risk of contamination is minimal
DISSOLVED O2: high O2, sparging or incr aeration can affect if interrupted
NITROGEN SOURCE: addition of ammonium stimulates overproduction, molasses isgood source of nitrogen
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Citric acid production
Surface fermentation submerged fermentation
Solid liquid Stirred AirliftBioreactor bioreactor
N alkanes (C9-C23) can also be used to produce citric acid; canresult in excess production of isocitric acid
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ACETIC ACID: industrial uses
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ACETIC ACID
Vinegar is prepared from alcoholic liquids since ceturies
CH3 CH2OH---- CH3CHO-------- CH3CH(OH)2 ------- CH3COOHEthanol acetaldehyde acetaldehyde hydrate acetic acid
NAD+ NADH +H+ NADP+ NADP +H+
Alcoholdehydrogenase Acetaldehyde dehydrogenase
Gluconobacter, Acetobacter with acid tolerant A. aceti
Incomplete oxidation of ethanol
One molecule of ethanol one molecule of acetic acid is produced12% acetic acid from 12% alcohol
It is an obligate anaerobe, Gram-positive, spore-forming, rod-shaped,thermophilic organism with anoptimum growth temperature of 55–60 o C and optimum pH of 6.6–6.8.
Clostridium thermoaceticum
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VINEGAR: 4% by volume acetic acid with alcohol, salts, sugars and estersflauoring agent in sauces and ketchups, preservative also
Wine, malt, whey (surface or submerged fermentation process)
Surface: trickling generator; fermentale material sprayed over surface, trickle throshavings contaning acetic acid producing bacteria; 30oC (upper) and 35oC (lower).Produced in 3 days.
Submerged: stainless steel, aerated using suction pump, production is 10X higher
Clostridium thermoaceticum (from horse manure) is also able to utilize five-carbon sugars:
2C5H10O5 --- 5CH3COOH
A variety of substrates, including fructose, xylose, lactate, formate, andpyruvate, have been used as carbon sources in an effort to lower substratecosts. This factor is also important if cellulosic renewable resources are to beused as raw materials.Typical acidogenic bacteria are Clostridium aceticum, C. thermoaceticum,Clostridium formicoaceticum, and Acetobacterium woodii. Many can also reducecarbon dioxide and other one-carbon compounds to acetate.
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These enzymes are metalloproteins; for example,CODH contains nickel, iron, and sulfur; FDHcontains iron, selenium, tungsten, and a smallquantity of molybdenum; and the corrinoid enzyme(vitamin B12 compound) contains cobalt. C.thermoaceticum does not have any specific aminoacid requirement; nicotinic acid is the sole essentialvitamin
1mol
2moles
2moles
1mol
1molCODH
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LACTIC ACID: industrial uses
Technical grade
20-50%
Ester manufactureTextile industry
Food grade>80%
Food additive (sour flour and dough)
Pharmaceutical grade
>90%
Intestinal treatment(metal ion lactates)
Glucose
G3P NAD+
NADH +H+1,3-biphosphoglycerate
G3P dehy-drogenase
Pyruvate
Lactic acid
LDH(Lactate dehydrogenase)
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LACTIC ACID
2 isomeric forms L(+) and D(-) and as racemic mixture DL-lactic acidFirst isolated from milkToady produced microbial
Heterofermentation Homofermentation
Other than lactate products only lactate as product
Lactobacillus
L. delbrueckii GlucoseL. leichmanni
L. bulgaricusL.helvetii Whey (lactose)
L.lactis ------- MaltoseL.amylophilus -------- StarchL.pentosus ------ Sulfite waste liquor
Mostly one isomer is produced
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LACTIC ACID: production process
Fermentation broth (12-15% glucose, N2, PO4, salts micronutrients)pH 5.5-6.5/temp 45-50oC/75h
Heat to dissolve Ca lactate
Addition of H2SO4(removal of Ca SO4)
Filter and concentrate
Addtion of Hexacyanoferrant(removes heavy metal)
Purification (Ion exchange)
Concentration
Lactic acid
1mol of glucose gives 2 moles of lactic acid; L lactic acid is predominantly produced
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GLUCONIC ACID: Applications
1. Used in stainless steel manufacturing, leather (can remove rust andcalcareous deposits)
2. Food additive for breverages3. Used in Ca and Fe therapy4. Na gluconate used in sequestering agent in detergets5. Desizing polyester or polyamide fabric6. Manufacture of frost and cracking resistant concrete
Bacteria: Gluconobacter, Acetobacter, Pseudomonas, VibrioFungi: Aspergillus, Penicillium, Gliocladium
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D-Glucose D-gluconolactone Gluconic Acid
PQQPQQH2
Glucose dehydrogenase
PQQ: pyrroliquinoline quinonecoenzyme
Bacteria
Fungi FAD FADH2
O2H2O2
Glucose oxidase
Catalase
Lactonase
H2O
fungi
intracellular extracellular
ExtracellularInducible
High conc of glucose and pH above 4H2O2 antagonist for other micro-organisms
Submerged fermentation processUse glucose from cornH 4.5-6.528-30oC for 24hIncr supply of O2 enhances yield
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ITACNIC ACID: Applications
1. Used in plastic industry, paper industry2. Manufacturing of adhesives
Aspergillus itoconicus and A.terreus
Cis-aconitic acid undergoes decarboxylation
Itaconic acid Itatartaric acid
(-) By Ca to incr yield
Itaconic acid Oxidase
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SECONDARY METABOLITES
ANTIBIOTICS
BROAD SPECTRUM NARROW SPECTRUM
Control growth ofwide range ofunrelated organismsTet, Cm
Control growth ofselected number oforganismsPen, Str
Streptomyces,eg. Tetracyclin, actinomycin D,
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ANTIBIOTICS: applications
1. Antimicrobial agents for chemotherapy2. Antitumour antibiotics eg. Actinomycin D and mitomycin D3. Food preservative antibiotics eg in canning (chlortetracycline) or fish or meat
preservation (pimarcin, nisin)4. Antibiotics in animal feed and veterinary medicine eg enduracidin, tylosin and
hygromycin B, theostrepton, salinomycin5. Control of plant diseases eg blasticidin, teranactin, polyoxin6. Molecular biology
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MODE OF ACTION OF ANTIBIOTICS
DNA
RNARIBOSOMES
PABA
DHF
THF
CELL WALL SYNTHESIS
DNA GYRASERNA ELONGATION
DNA DIRECTED RNA POLYMERASE
PROTEIN SYNTHESIS(50S INHIBITORS)
PROTEIN SYNTHESIS(30S INHIBITORS)
PROTEIN SYNTHESIS(tRNA)
LIPID BIOSYNTHESIS
CYTOPLASMIC MEMBRANE STRUCTUREAND FUNCTION
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SYTHETIC ANTIBIOTICS
Selective toxicity: concept, Paul Ehrlich
1. GROWTH FACTOR ANALOGS:structurally similar to a growth factor required in a micro-organism;
small differences of analogs in authentic growth factor prevent analog tofunction in the cell.
A. SULFA DRUGS: specifically inhibit bacteria (streptococcal infections)eg. SULFANILAMIDE: is an analog of PABA (p-aminobenzoic acid) which ispart of folic acid and nucleic acid precursor. Combination:sulfamethoxazole and trimethoprim; disadvantages and advantages
B. ISONIAZID: important growth factor with narrow spectrum only againstMycobacterium. It interferes with synthesis of mycolic acids, a cell wallcomponent. It is an analog of nicotinamide (vitamin). Single most effectivedrug against tuberculosis.
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2. NUCLEIC ACID BASE ANALOGS
URACIL 5-FLOUROURACIL (Uracil analog)PHENYLALANINE p-FLOUROPHENYLALANINETHYMINE 5-BROMOURACIL (thymine analog)
Addition of F or Br does not alter the shape but changes chemical propertiessuch that the compound does not function in the cell metabolism, therebyblocking the nucleic acid synthesis.These analogs are used in treatment of viral and fungal infections and many ofthese occur as mutagens.
3. QUINOLONES:Antibacterial compounds interfere with bacterial DNA gyrase, preventsupercoiling (packaging of DNA) eg Flouroquinolones like ciprofloxin (UTI,anthrax). B. anthracis maybe resistant to pencillin. These are effective in bothG+ve and G-ve bacteria since DNA gyrase is present in all.Also used in beef and poultry for prevention and treatment of respiratorydiseases.
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Ouinolones
New generation Flouroquinolnes
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NATURALLY OCCURING ANTIBIOTICS
FROM BACTERIA, FUNGILESS THAN 1% OF 1000S OF ANTIBIOTICS ARE USEFUL BECAUSE OF TOXICITYOR LACK OF UPTAKE BY HOST CELLSNatural antibiotics can be artificially modified to enhance their efficacy then they are
semi-synthetic antibiotics
Broad spectrum antibiotics: effective against both gram +ve and gram-veNarrow may also be beneficial to target specific group of bacteria eg. Vancomycin:narrow spectrum effective for gram positive pencillin resistant Staphylococcus,Bacillus, Clostridium
Targets for antibiotics mayberibosomes (Cm and Str for Bacteria and Cyclohexamide for eukarya), Cell
wall, cytoplasmic membrane, lipid biosynthesis, enzymes, DNA replication andtranscription elements
Protein synthesis, Transcription (RNA poly, RNA elongation etc)
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Produced By Fungi
B-LACTAMS (b-lactam ring)
Penicillin
Cephalosporins
Produced by Prokaryotes
AMINOGLYCOSIDES (amino sugars with glycosidic linkage)
MACROLIDES (lactone ring bonded to sugars)
TETRACYLINES (Streptomyces)
PEPTIDE ANTIBIOTICS (Daptomycin, (Streptomyces)
PLATENSIMYSIN (Streptomyces)
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1. PENICILLINS, 2. CEPHALOSPORINS, 3. MONOBACTAMS AND 4. CARBAPENEMS
Beta Lactam Antibiotics
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PENCILLIN--------b-LACTAM ANTIBIOTIC
Pencillin G and V (natural)Penicillium chrysogenumAlexander Fleming
Used for PneumococcalStreptococcal infections
Pencillin G first clinically useful antibioticFor Gram positive bacteria
6-AMINOPENICILLIANIC ACID
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Ampicillin, carbencillin
Slight modification in N-acyl groups results in semi synthetic penicillin which is able toact on gram negative bacteria (goes past outer membrane) to act on cell wall
MANY BACTERIA HAVE BETA LACTAMASE HENCE THOSE BACTERIA AREPENCILLIN RESISTANTEG. Oxacillin and Methicillin beta lactamase resistant semi synthetic antibiotics
MECHANISM OF ACTION
• Pencillins block cell wall synthesis: transpeptidation (cross linking 2 glycan peptide chains)
• Transpeptidases bind to pencillin hence they are called PENCILLIN BINDING PROTEINS (PBP)
• Newly synthesized bacterial wall is no longer cross linked and has poor strength• PBP also stimulates release of AUTOLYSINS (ENZYMES TO DIGEST CELL WALL)• Osmotic pressure differences cause lysis
• VANCOMYCIN: does not bind PBPs but D-alanyl- Dalanine peptide to block transpeptidation
• BECAUSE OF SELECTIVE PROCESS B-LACTAMS DO NOT AFFTECT HOST CELLS AND MECHANISM IS UNIQUE TO BACTERIA
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MECHANISM OF ACTION
Natural penicillin: i.e. V and G are effective against several gram positive bacteriaThey are effective against b-lactamase producing MO (enz which can hydrolyze penicillins)
Eg. Staphylococcus aureus
Production of penicillin is used: 45% (human), 15% (animal health) and 45% for production of semi synthetic penicillin
P. notatum, P.chrysogenum and its mutant strain which is a high yeilding strain (Q176)Genetically engineered strains for improved pencillin production are being used now
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UDP deriv of NAM and NAG are synthesized
Sequentially aa are added to UDP-NAM to form NAM -pentapeptideATP is used, no tRNA or ribosomes involved in peptide bond formation
Transfer of UDP-NAM-pentapeptideto bactoprenol PO4
UDP tansfers NAG to bactoprenol-NAM peptapeptide. For pentaglycine use special glycyl-tRNA moc but not ribosomes Transport of completed NAM-
NAG-pepntapeptide across membrane
Attached to growing end of PG chain and incr by one repeat unit
Bactoprenol carrier moves back across membrane by losing one PO4 for a new cycle
LIPID I LIPID II
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UDP glucose
Bactoprenol is a 55 carbon alcohol and linked to NAM by pyrophosphate
In S. aureus pepntapeptide has L-lys and in E. coli DAP
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Final step is TRANSPEPTIDATION which creates peptide cross links between PGchains. The enzyme removes terminal D-alanine as cross link is formed
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The b-lactam group of antibiotics includes an enormous diversity of naturaland semi-synthetic compounds that inhibit several enzymes associated with the finalstep of peptidoglycan synthesis.All of this enormous family are derived from a b-lactam structure: a four-memberedring in which the b-lactam bond resembles a peptide bond. The multitude of chemicalmodifications based on this four-membered ring permits the astonishing array ofantibacterial and pharmacological properties within this valuable family ofantibiotics.
Clinically useful families of b-lactam compounds include the penicillins,cephalosporins, monobactams and carbapenems. Many new variants on the b-lactamtheme are currently being explored. Certain b-lactams have limited use directly astherapeutic agents, but may be used in combination with other b-lactams to act asb-lactamase inhibitors.
Co-amoxyclav, for example is a combination of amoxycillin and the b-lactamase inhibitor clavulanic acid. During cross-linking of the peptidoglycanpolymer, one D-alanine residue is cleaved from the peptidoglycan precursor andthis reaction is prevented by b-lactam drugs.
More recent studies have shown that the activity of this class of drugs is morecomplicated and involves other processes as well as preventing cross-linking ofpeptidoglycan.
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An increasing number of bacteria are penicillin resistant. Penicillinase-resistant
penicillins such as methicillin, nafcillin, and oxacillin are frequently employed
against these bacterial pathogens.
Although penicillins are the least toxic of the antibiotics, about 1 to 5% of the
adults in the United States are allergic to them. Occasionally a person will die of a
violent allergic re- sponse; therefore patients should be questioned about penicillin
allergies before treatment is begun.
B-lactamase
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MRSAVRSA
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CEPHALOSPORINS
cefatrioxone
B-lactam ring Dihydrothiazine ring (6 member)
Same mode of action with broader spectrum than penicillinsResistant to b-lactamasesHence used to treat infections which are penicillin resistantUsed to treat Nesseria gonorrhea (STD)
Cephalosporium: Cephalosporin C
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Most cephalosporins (including cephalothin, cefoxitin, ceftri- axone,and cefoperazone) are administered parenterally.Cefoperazone is resistant to destruction by b-lactamases andeffective against many gram-negative bacteria, including Pseudomonasaeruginosa.Cephalexine and cefixime are given orally rather than by injection.
7-ACA: 7- aminocephalosporanic acid nucleus structure in all cephalosporins
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G+ > G- G+ = G-
G+ < G-
R1R2
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TETRACYCLINES
• Broad spectrum• Effective for G+ and G- (mycoplasmas, rickettesia, chlamydia)• Used for combatting stomach ulcer (Helicobacter pylori)• Inhibit protein synthesis by blocking binding of amino acyl tRNA to ribosome (A site)
BASIC STRUCTURE
• Napthacene ring• Chlortetracycline and oxytetracycline are most commonly used in human and veterinary
diseases and for preservation of meat, fish and poultry
Three members of the tetracycline family.Tetracycline lacks both of the groups that areshaded. Chlortetracycline (aureomycin) differsfrom tetracycline in having a chlorine atom(blue); doxycycline consists of tetracyclinewith an extra hydroxyl (purple).
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TETRACYCLINES Streptomyces aureofaciens20 diff species producing mix of tetGenetic modificationPolyketide synthesis
Antibiotics synthesized by successive condensation of small carboxylic acidsLike acetate, butyrate, propionate, malonate
High doses of tetracycline may result in nausea, diarrhea, yellowing of teeth in children, and damage to the liver and kidneys.
Str. aureus. S.flavusS. rimosus, S. antibioticus
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AMINOGLYCOSIDESOligosaccharide antibiotics
Streptomycin, kanamycin, neomycin, and tobramycin are synthesized byStreptomyces, whereas gentamicin comes from a related bacterium,Micromonospora purpurea.
Known as reserve antibiotics as they develop resistance quickly
• Structurally all contain a cyclohexane ring and amino sugars bound by glycosidiclinkages
• Bind to the 30S small ribosomal subunit and interfere with protein synthesis in at leasttwo ways. They directly inhibit protein synthesis and also cause misreading of thegenetic message carried by mRNA…prolonged use can cause kidney damage and hearingloss
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AMINOGLYCOSIDES producing organisms
Streptomycin Streptomyces griesus
Neomycin B and C S.fradiae
Kanamycin A, B and C S.kanamyceticus
Hygromycin B S.hygroscopicus
Gentamycin Micromonospora purpurea
Sisimicin M.inyoensis
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MACROLIDES
Antibiotics with a large lactone ring (macrocyclic lactone ring)Which consists of 12-, 14- and 16-membered lactone rings with 1-3 sugars linked
by glycosidic bondEffective agaist penicillin resistant MO, G+ org, inhibitb y binding to 50S
ribosome
Erythromycin : Streptomyces erythreus14-membred connected to 2 sugarsGenetic modifications by polyketide synthesis
Clarithromycin (Erythromycin derv)Used to treat stomach ulcers
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MACROLIDES
Polyene macrolides: lactone rings in range of 26-28Eg. Nystatin, amphotericin
Actinomycetes are most common organisms which produce them
Erythromycin is a relatively broad-spectrum antibiotic effective against gram-positive bacteria, mycoplasmas, and a few gram-negative bacteria. It is usedwith patients allergic to penicillins and in the treatment of whooping cough,diphtheria, diarrhea caused by Campylobacter, and pneumonia from Legionellaor Mycoplasma infections.
Newer macrolides are now in use.Clindamycin is effective against a variety of bacteria including staphylococciand anaerobes such as Bacteroides.Azithromycin is particularly effective against Chlamydia trachomatis.
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AROMATIC ANTIBIOTICS
CHLORAMPHENICOL
Aromatic rings in structureChloroamphenicol, griesofluvin, novobiocin
Broad spectrum antibiotic against G+ and G- bacteria, rickettesia, chlamydia, actinomycetes
chloramphenicol binds to 23S rRNA on the 50S ribosomal subunit. It inhibits the peptidyl transferase and is bacteriostatic.
Streptomyces venezuelae and S.omiyanesis
GRIESOFULVIN
This antibiotic has a very broad spectrum of activity but unfortunately is quite toxic. One may see allergic responses orneurotoxic reactions. The most common side effect is a temporary or permanent depression of bone marrow function, leadingto aplastic anemia and a decreased number of blood leukocytes. Chloramphenicol is used only in life-threatening situationswhen no other drug is adequate.
Maybe attacks chitin biosynthesis hence acts as anti fungal antibiotic
Penicillium patulum
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PEPTIDE ANTIBIOTICS
Following a 40-year hiatus in discovering new classes of antibacterial compounds,three new classes of antibacterial antibiotics have been brought into clinical use:
Cyclic lipopeptides (Daptomycin), Glycylcyclines (tigecycline) and Oxazolidinones(Linezolid)
Daptomycin : Streptomyces roseosporus used to treat MDR infections
Tigecycline: Tygacil® marketed by Wyeth used to treat MDR strains ofStaphylococcus aureus and Acineotobacter baumanii. Mechanism similar to
tetracycline.
Also shows suceptibility to NDML (New Delhi metallo-b-lactamase multidrugresistant Enterobacteriaceae)
NDML is an enzyme which makes bacteria resistant to broad range of b-lactam antibiotics.This includes antibiotics of carbapenems for treatment of antibiotics resistant infections.
Termed as “SUPERBUGS” Such bacteria susceptible to polymixins and tigecyclines
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MECHANISM OF DRUG RESISTANCE
PlasmidsR-PlasmidsSuperinfection: Clostridium difficile, Candida albicansTransformation, conjugation, transduction, ABC transportersPhage therapy
There has been some recent progress in developing new antibiotics that areeffective against drug-resistant pathogens.
Two new drugs are fairly effective against vancomycin-resistant enterococci.Synercid is a mixture of the streptogramin antibiotics quinupristin and dalfopristinthat inhibits protein synthesis.A second drug, linezolid (Zyvox), is the first drug in a new family of antibiotics, theoxazolidinones. It inhibits protein synthesis and is active against both vancomycin-resistant enterococci and methicillin-resistant Staphylococcus aureus.