Microbial GrowthF08

Microbial growthf08

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: M I CROBI AL GROWT H Cha pter 6 About GROWT H ......... • Usual l y means an i ncr ease i n si ze however ….. • M i cr obes gr ow by i ncr easi ng i n number and not i n si ze • They can accumul ate i nto cl umps of hundr eds and col oni es of thousands • COLON I ES = l ar ge number of mi cr obes usual l y d er i ved fr om one or gani sm (cl one) • Uni cel l ul ar or gani sms do gr ow i n si ze but ONL Y u nti l the m other cel l d oubl es i n si ze and d upl i cates i ts contents • The mother cel l di vi des i nto 2 new d a ughter cel l s • T hi s pr ocess i s ca l l ed bi na r y fi ssi on G ROWT H REQU I REM EN T S – Obl i ga te vs fa cul ta ti ve: – Obl i gate: must have the speci fi c envi r onment – Facul tati ve: abl e to adjust to fl uctuati ons or a r ange of envi r onmental factor s • PH YSI CAL REQU I REM EN T S 1. pH 2. TEM PERATURE 3. OSM OTI C PRESSURE • BI OCH EM I CAL REQU I REM EN T S 1. C and N sour ces 2. H 2O and Oxygen r equi r ements 3. Or gani c gr owth factor s & tr ace mi ner al s T EM PERAT U RE • • T emper a tur e r a nge – M i ni mum, OPTI M UM , M axi mum Psychr ophi l es: col d l ovi ng 0-15 °C – Opti mum: 15 - 30 °C – Psychr otr ophs: mai nl y r esponsi bl e for food spoi l age • • M esophi l es: moder ate temp. l ovi ng 10-47 °C – Opti mum: 25-45 °C T her mophi l es: heat l ovi ng 40-80 °C – Opti mum: 50-60 °C – Extr eme ther mophi l es: 65-110 °C T ypi ca l Gr owth Ra tes a nd T emper a tur e Figure 6.1 pH • BU FFERS: stabi l i zes pH of a sol uti on – Abl e to take up or donate H + t o the sol uti on • OPT I M U M f or most bacter i a = pH 6.5-7.5 • Nor mal human physi ol ogi cal pH • N eutr ophi l es • ACI D OPH I LES - can gr ow at l ow pH – L ower than pH 4.0 • ALKALI PH I LES - can gr ow at hi gh pH • OPT I M U M f or yeast = pH 4.0 - 5.0 3. OSM OT I C PRESSU RE • For ce wi th whi ch a sol vent moves fr om a sol uti on of l ower sol ute concentr ati on to sol uti on of hi gher sol ute concentr ati on • H YPERT ON I C sol uti on: conc. of sol utes outsi de > i nsi de – Pl asmol ysi s occur s, wa...
View Full Document

Ask a homework question - tutors are online