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Bacteria?!!Sir azrimi1111Bacterial GroupsMost widely accepted taxonomic classification for bacteria is Bergeys Manual of Systematic Bacteriology.5000 bacterial species identified, 3100 classified.Bacteria are divided into four divisions (phyla) according to the characteristics of their cell walls.Each division is divided into sections according to:Gram stain reactionCell shapeCell arrangementsOxygen requirementsMotilityNutritional and metabolic propertiesEach section contains several genera.2111Classification of Bacteria

Four Divisions of Bacteria

MORPHOLOGYBacteria grow tremendously fast when supplied with an abundance of nutrients. Different types of bacteria will produce different-looking colonies, some colonies may be colored, some colonies are circular in shape, and others are irregular. The characteristics of a colony (shape, size, pigmentation, etc.) are termed the colony morphology. Colony morphology is a way scientists can identify bacteria.

7WHAT CAN GROW ON AGAR PLATE?Streptococcus pyogenesBacteria: Each distinct circular colony should represent an individual bacterial cell or group that has divided repeatedly. Being kept in one place, the resulting cells have accumulated to form a visible patch. Most bacterial colonies appear white, cream, or yellow in color, and fairly circular in shape. For example:

BACTERIAEach distinct circular colony should represent an individual bacterial cell or group that has divided repeatedly. Being kept in one place, the resulting cells have accumulated to form a visible patch. Most bacterial colonies appear white, cream, or yellow in color, and fairly circular in shape

Bacillus subtilisProteus vulgarisYeasts: Yeast colonies generally look similar to bacterial colonies. Some species, such as Candida, can grow as white patches with a glossy surfaceCandida Albicans) is a type of yeast that can grow on the surface of skin(7)

Molds are actually fungi, and they often appear whitish grey, with fuzzy edges. They usually turn into a different color, from the center outwards. Two examples of molds are shown below: Green Mold (Trichoderma harzianum)Black Mold (Aspergillus nidulaus)

Structure of BacteriaSize of BacteriaAverage bacteria 0.5 - 2.0 um in diam.RBC is 7.5 um in diam.Surface Area ~12 um^2Volume is ~4 umSurface Area to Volume is 3:1Typical Eukaryote Cell SA/Vol is 0.3:1Food enters through SA, quickly reaches all parts of bacteriaEukaroytes need structures & organellesChapter 4Shapes of BacteriaCoccusChain =Cluster =BacillusChain =CoccobacillusVibrio = curved????Chapter 414Chapter 4

StructuresFlagella PiliCapsulePlasma MembraneCytoplasmCell WallLipopolysaccharidesTeichoic AcidsInclusionsSporesChapter 4

FlagellaMotility - movementSwarming occurs with some bacteriaSpread across Petri DishProteus species most evidentArrangement basis for classificationMonotrichous; 1 flagellaLophotrichous; tuft at one endAmphitrichous; both endsPeritrichous; all around bacteriaObserve Picture in Micro Lab.Chapter 4Chapter 4

Chapter 4Mono- or Lophotrichorus Chapter 4

PiliShort protein appendagessmaller than flagellaAdhere bacteria to surfacesE. coli has numerous typesK88, K99, F41, etc.Antibodies to will block adheranceF-pilus; used in conjugationExchange of genetic informationFlotation; increase boyancyPellicle (scum on water)More oxygen on surfaceChapter 4F-Pilus for ConjugationChapter 4

Capsule or Slime LayerGlycocalyx - Polysaccharide on external surfaceAdhere bacteria to surfaceS. mutans and enamel of teethPrevents PhagocytosisComplement cant penetrate sugarsChapter 4Cytoplasm80% Water {20% Salts-Proteins)Osmotic Shock importantDNA is circular, HaploidAdvantages of 1N DNA over 2N DNAMore efficient; grows quickerMutations allow adaptation to environment quickerPlasmids; extra circular DNAAntibiotic ResistanceNo organelles (Mitochondria, Golgi, etc.)Chapter 4Cell MembraneBilayer PhospholipidWater can penetrateFlexibleNot strong, ruptures easilyOsmotic Pressure created by cytoplasm

Chapter 4Chapter 4

Chapter 4

Chapter 4

Chapter 4Cell Wall Peptido-glycan Polymer (amino acids + sugars)Unique to bacteriaSugars; NAG & NAMN-acetylglucosamineN-acetymuramic acidD form of Amino acids used not L formHard to break down D formAmino acids cross link NAG & NAMChapter 4

Chapter 4

Chapter 4

Chapter 4

Chapter 4

Chapter 4

Cell Wall SummaryDetermine shape of bacteriaStrength prevents osmotic rupture20-40% of bacteriaUnique to bacteriaSome antibiotics effect directlyPenicillinChapter 4Chapter 4Video Clip on Cell Wall

Teichoic AcidsGram + onlyGlycerol, Phosphates, & RibitolAttachment for PhagesChapter 4Chapter 4

40Chapter 4Lipopolysaccharide (LPS)Endotoxin or PyrogenFever causingToxin nomenclatureEndo- part of bacteriaExo- excreted into environmentStructureLipid APolysaccharideO Antigen of E. coli, SalmonellaG- bacteria onlyAlcohol/Acetone removesChapter 4

Chapter 4

LPS (contd)FunctionsToxic; kills mice, pigs, humansG- septicemia; death due to LPSPyrogen; causes feverDPT vaccination always causes feversAdjuvant; stimulates immunityHeat Resistant; hard to removeDetection (all topical & IV products)Rabbits (measure fever)Horse shoe crab (Amoebocytes Lyse in presence of LPS)Chapter 4LPS (contd.)Appearance of ColoniesMucoid = Smooth (lots of LPS or capsule)Dry = Rough (little LPS or capsule)O Antigen of Salmonella and E. coli2,000 different O Ags of Salmonella100s different O Ags of E. coliE. coli O157O Ags differ in Sugars, not Lipid AChapter 4EndosporesResistant structureHeat, irradiation, coldBoiling >1 hr still viableTakes time and energy to make sporesLocation important in classificationCentral, Subterminal, TerminalBacillus stearothermophilus -sporesUsed for quality control of heat sterilization equipmentBacillus anthracis - spores Used in biological warfareChapter 4Chapter 4

Chapter 4

G+ vs. G-G+Thicker cell wallTeichoic Acids

G-Endotoxin - LPS

Which are more sensitive to Penicllin?Alcohol/Acetone affects which more?Chapter 4Prokaryotes vs. EukaryotesCell WallTeichoic AcidsLPSEndosporesCircular DNAPlasmidsChapter 4