Module 4. Chapter 6 Microbial Growth

Transcription

1 Mdule 4 Chapter 6 Micrbial Grwth Micrbial grwth refers t increase in, nt Grwing micrbes means an increase in Imprtant t understand cnditins necessary fr micrbial grwth The requirements fr grwth Physical requirements Chemical requirements Temperature Micrbes grw within temperature range Lw, high temp affect Minimum grwth temp Optimum grwth temp Maximum grwth temp - Micrbes divided int 5 grups Psychrphiles Psychrtrphs Mesphiles Thermphiles Hyperthermphiles Psychrphiles Can grw belw C, ptimum at C Usually by temperatures abve C Psychrtrphs Can grw at C, ptimum at C Cause prblems with, can grw But grw à prper helps prevent Mesphiles Many grw best at C Mesphiles include mst cmmn, fd rganisms

2 Thermphiles, hyperthermphiles Grw is, vlcanic Cannt grw belw C usually nt prblem ph ph refers t cncentratin f Lw ph à à High ph à à Mst bacteria grw best near grw in acidic envirnments, are prducts f acidphiles Preserved frm by bacterial and can grw between ph 5 and 6 Osmtic Pressure Micrbes dependent n t carry nutrients Micrbes live in envirnments envirnments causes water t cell Grwth inhibited due t Fd preserved by high smtic pressure - add tlerate high smtic pressure Extreme halphiles high salt cnditins Live in the Dead Sea, salt lakes Chemical Requirements Carbn Structural rganic mlecule, surce use rganic carbn surces use CO 2 Nitrgen In, prteins, Mst bacteria decmpse Sme bacteria use r A few bacteria use frm atmsphere Called Sulfur In, thiamine, and bitin Mst bacteria decmpse Sme bacteria use r Phsphrus In, RNA, ATP, and is a surce f phsphrus Trace elements elements required in amunts Usually as

3 Organic grwth factrs Organic cmpunds btained Vitamins, amin acids,, Oxygen metablism prvides mre energy than metablism BUT, Oxygen is in high amunts t ALL rganisms frms f xygen are highly reactive; cell cmpnents Many metablic pathways exist t Singlet xygen, 1 O Superxide free radicals, O 2 - enzyme neutralizes free radicals Perxide anin, O 2 2- Neutralized by and enzymes Hydrxyl radicals, OH - - Obligate aerbes Grw where ccurs Have that O 2 Facultative anaerbes Grw with grwth via r Obligate anaerbes t detxify Grw than Aertlerant anaerbes Obligate, prduce that inhibit cmpetitin frm Pssess enzymes t Micraerphiles detxify high cncentratins f Bifilms that hlds f bacteria tgether Share Sheltered frm is a created by an extracellular plysaccharide Frmed by species in muth Only when is present Plaque allws ther micrbes t Frm that lead t tth decay, gum disease Bifilms ften frm n and ther tubing Numbers are ften t lw t detect Bifilm prtects bacteria frm Can grw rapidly nce inside bdy, causing and ther infectins

4 Grwing Micrbes in the Lab : prepared fr micrbial : n micrbes : f micrbes (the ) int sterile medium : micrbes grwing in/n culture medium Agar Cmplex Used as fr culture media in Petri plates, slants, and deeps Generally nt by micrbes Liquefies at 100 C Slidifies at ~40 C Culture Media Chemically defined media: exact chemical cmpsitin Cmplex media: extracts and digests f yeasts, meat, r plants f nutrients Bisafety Levels BSL-1: precautins BSL-2:, glves, eye BSL-3: cabinets t prevent BSL-4: sealed, pressure is twice The Grwth f Bacterial Cultures Recall, micrbial grwth is increase in Bacteria reprduce by A single splits int cells Sme micrbes reprduce by Small grwth ( ) gets larger, and Generatin time, the time it takes fr a Essentially, time it takes fr Varies amng species Can be 20 mins, can be 20 days Micrbes can grw in ideal cnditins Eg, if g =, then: 1 cell à 1 in generatins, 1 cell à 1 in generatins, Bacterial grwth pltted n Numbers fr linear r arithmetic graph scale increases in increments f 10, 100, 1,000, 10,000, etc Cnverts rapidly increasing expnential grwth frm line int line

5 Phases f grwth Bacteria grwing in liquid have characteristic grwth pattern When pltted n lgarithmic graph The Lag Phase The Lg Phase The Statinary Phase The Death Phase Measurements f Bacterial Grwth Bacterial cultures are quantified by tw general types f measurements measurements measure Indirect Measurements use measures t determine ppulatin size Direct measurement f micrbial grwth Standard Plate Cunts Grwth micrbial sample n Cunt 1 = 1 Advantages Only cunted Obtain Disadvantage Takes fr clnies t frm intensive Filtratin is passed thrugh retained n is transferred t Useful when f bacteria in sample Often used t detect bacterial cntaminatin f Mst prbable number (MPN) methd tube MPN test sample Cunt tubes with Useful when bacteria But, numbers are % accurate

6 Direct micrscpic cunt Numbers f micrbes cunted results, but difficult t cunt cells lk like cells Need t cunt accurately Indirect measurement f micrbial grwth Turbidity, r, f a liquid culture Detected using a Higher, increased and methd f btaining quantity, but. D nt btain - values are nly meaningful when t each ther cells cntribute t just like cells Metablic activity Assumes f bacteria prduces r metablic prduct Eg, measure build up Can be useful when cells Can be perfrmed withut needing t micrbes Dry weight Remval f micrbes frm grwth medium, Useful fr