ESR - FM 3 Structure Cells, Flagella, Dll

Lecture 3Overview of cell structure and significance of smallnessCytoplasmic membrane: structureCytoplasmic membrane: functionCell wall of prokaryotes: peptidoglycanOuter membrane of gram negative bacteriaCell wall synthesis and cell divisionArrangement of DNA in prokaryotes

Endang S. Rahayu Fak Teknologi Pertanian UGM

Mikrobia pada makananSpiralBacteriaRod-ShapedBacteriaMoldsYeastStaph aureusCocciBacteriaC. botulinumListeriaE.coli 0157:H7Salmonella


Sel prokariot dan eukariot


Bakteri Sel tunggal (uniseluler)Tidak memiliki membran inti (prokariot)Bentuk :Bulat (cocci) dengan ukuran 0.4-1.5 mContoh : Staphylococci (kluster seperti buah anggur) Streptococci (berantai)Batang (rods) dengan ukuran 0.25-1.0 m atau 0.5-6.0 mContoh : bacilli (batang lurus)Spirilla (batang spiral)


EndosporaBeberapa bakteri mampu membentuk endospora Endospora dihasilkan saat bakteri mengalami stress lingkungan seperti kekurangan nutrisi, kekeringan, dsb.Endospora digunakan untuk mempertahankan diriEndospora tidak melakukan metabolisme (berada dalam bentuk dorman) dan tahan terhadap suhu tinggi, disinfektan, sinar UVSaat kondisi lingkungan membaik, endospora melakukan germinasi dan tumbuh menjadi sel bakteriContoh bakteri penghasil endospora : Bacillus dan ClostridiumDiperlukan sterilisasi untuk membunuh sporaSpora Clostridium Spora Bacillus


Endospora


Bakteri - Reproduksi / Berkembang biakAseksual melalui pembelahan sel (fission)Waktu ganda (waktu generasi) : 20 menitSatu sel setelah 11 jam dapat menjadi 1,0 x 106Namun demikian di alam pertumbuhan bakteri dibatasi oleh kekurangan nutrisi, akumulasi toksin dan metabolit, suhu yang tidak sesuai, kekeringan, dllJumlah maksimum bakteri 1x109 CFU/g atau ml CFU - Colony Forming Unit


Reproduction Binary fission12 4 8 16 32 64 128Millions


Waktu yang diperlukan bakteri untuk tumbuhDalam kondisi ideal, beberapa bakteri dapat melakukan duplikasi dalam waktu 15-30 menitContoh bakteri dengan doubling time 20 menitSTART20 menit40 menit1 jam


Latihan (diasumsikan waktu ganda =20 menit)1 bakteri terdapat pada hamburger dengan suhu kamar (30 C) Berapa jumlah bakteri setelah 1 jam? 4 jam? 8 jam?Apa yang terjadi jika jumlah bakteri awal pada hamburger tersebut adalah 10.000 ?


Yeast Ukuran lebih besar dari bakteriMemiliki membran inti (eukariot)Uniseluler (bentuk : bulat, elip, silinder, 5-8 mPseudohifa


Yeast - ReproduksiAseksual :Fission : pembelahan sel

Budding : pembentukan tunasSeksual :Pembentukan spora


MoldBerfilamen, multiseluler, ukuran lebih besar dari bakteri dan yeast (10-40 m)Hifa (masing-masing filamen)Miselia (kumpulan hifa)


Mold - ReproduksiAseksual :FragmentasiPembentukan spora aseksual (konidia, sporangium)Seksual :Pembentukan spora seksual


MoldsMucorRhizopusPenicilliumGeotrichumFusariumNeurosporaBotrytisAlternariaAspergillusPenicillium


MoldPertumbuhan Aw rendahInterval pH yang luasMesophilic and PsychrotrophicaerobSignificancePembusukanIndex sanitasiHealth IssuesMenghasilkan makanan


Different Shapes


Different Sizes


Surface Area vs. VolumeFig. 3.15Size affects rate of nutrient and waste transport across the cell membrane

Small size more efficient exchange, support of higher metabolic rate


Phospholipid BilayerFig. 3.16


Structure of Cytoplasmic MembraneFig. 3.18


Lipids in Bacteria and Archaea have different chemical bondsEster - BacteriaEther - ArchaeaFig. 3.20


Table 3.1 Comparative Permeability of Membranes to Various Molecules


Substance

Rate of Permeability

Water

100

Glycerol

0.1

Tryptophan

0.001

Glucose

0.001

Cl-

0.000001

K+

0.0000001

Fuction of Cytoplasmic MembranePermeability Barrieronly small, uncharged, hydrophobic molecules can pass through by diffusion (see Table 3.1)Protein Anchortransport, generation of energy, chemotaxisGeneration of proton motive force


Different types of transportAccumulation of solutes against the concentration gradientSpecificity


Cell Walls of BacteriaPeptidoglycan is found only in bacteriaKeeps cells from lysing, due to turgor pressure


Protoplast FormationHigh solute solutionLow solute solutionLysozyme -- a protein that breaks 1,4-glycosidic bonds in peptidoglycan


Peptidoglycan Structure


Peptidoglycan SheetGlycosidic linksPeptide cross-links


Teichoic AcidsAcidic polysaccharides found in gram positive cell walls


Gram Positive Cell Wall


Archaeal Pseudopeptidoglycan


Lipopolysaccharide (LPS)Only in gram negative bacteriaPart of the outer membrane


Gram Negative Outer MembranePorins - proteins that allow small molecules to cross membrane -- specific and non-specific


Cell Wall SynthesisCell wall is opened up by autolysins, and new peptidoglycan is deposited


Peptidoglycan SynthesisBactoprenol (a C55 isoprenoid alcohol) -- lipid carrier that transports dissacharide pentapeptide from cytoplasm to periplasm and inserts it into growing cell wallThe next step, transpeptidation, is inhibited by penicillin


Transpeptidation


Genome Size


Chromosomal DNA


Lecture 4.Flagella and motilityBacterial behavior: chemotaxis, phototaxisBacterial cell surface structures and cell inclusionsGas vesiclesEndospores


The Flagellum> 40 genes involved1000 H+ / rotation


Absence of chemical attractantPresence of chemical attractant chemical gradient sensed in a temporal manner


Other types of taxesphototaxis - lightaerotaxis - oxygenosmotaxis - osmotic strength


Cell structures and inclusionsfimbriae - aid cell adherence to surfacespili - conjugation, attachment to host cellglycocalyx - polysaccharide layer outside cell, attachment to host cells, protection from host immune system, resistance to dessicationpolyhydroxyalkanoate deposits - intracellular carbon and energy storepolyphosphate - intracellular reserveselemental sulfur - intracellular granulesmagnetosomes - intracellular magnetite crystals (iron oxide)gas vesicles - cell buoyancy


Poly--hydroxybutyrate (PHB)


Poly-3-hydroxybutyrate (PHB)Carbon and energy reserveAccumulates intracellularly when carbon source is not limiting for growthCan be utilized under carbon starvation conditionsBiodegradable bioplastics CH3OCHCH2C O[]n ~ 25,000


Gas Vesicle Proteinswatertight, gas-permeable structure(hydrophobic proteins)


EndosporesResistant to heat, radiation, acids, drying, chemicalsDo not contain RNADehydrated (only 10-30% H2O as vegetative cell)


Dipicolinic acidCharacteristic of endospores


How long can spores survive?See page 92, report that 25-40 million year old spores have been revivedThese spores were preserved in the gut of a bee that was trapped in amber


Problem in grainspH of 2.0 8.5 spoilage in acid products

Can grow at refrigeration temperatures, but low temps slow growth

SpoilageCan grow/spoil in lower Aw/higher NaCl content foods, but do not compete well with bacteria

Mycotoxin ProductionAFLATOXINS are concinogenicMainly produced on grain and nut productsFeeding high moisture corn to dairy cattle can cause aflatoxins to show up in milkAflatoxins Aspergillus Flavis carcinogenicRye Ergot Claviceps purpurea neurotoxin

Toxin effects carcinogenic, liver damage, neurotoxins, rashes, kidney damage

Mold Allergies

Sanitation IndexYeast and molds are less resistant to sanitizers therefore if they are present, sanitizers are not working

FoodsBlue cheese, Brie, Roquefort, Sake

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ESR - FM 3 Structure Cells, Flagella, Dll

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