Chapter 6 Microbial Growth

Module 4

Chapter 6 – Microbial Growth

· Microbial growth refers to increase in ______, not ______

o Growing microbes means an increase in ______

· Important to understand conditions necessary for microbial growth

The requirements for growth

· Physical requirements

· Chemical requirements

Temperature

· Microbes grow within ______temperature range

o Low, high temp affect ______

· Minimum growth temp –

· Optimum growth temp –

· Maximum growth temp -

· Microbes divided into 5 groups

o Psychrophiles –

o Psychrotrophs –

o Mesophiles –

o Thermophiles –

o Hyperthermophiles –

· Psychrophiles

o Can grow below ____ °C, optimum at ____ °C

o Usually ______by temperatures above ____ °C

· Psychrotrophs

o Can grow at ______°C, optimum at ______°C

o Cause problems with ______, can grow ______

§ But grow ______à proper ______helps prevent ______

· Mesophiles

o Many ______grow best at ____ °C

o Mesophiles include most common ______, food ______organisms

· Thermophiles, hyperthermophiles

o Grow is ______, volcanic ______

o Cannot grow below ____ °C – usually not ______problem

· pH refers to concentration of ______

o Low pH à ______à

o High pH à ______à

· Most bacteria grow best near ______

· ______grow in acidic environments

o ______, ______are products of acidophiles

o Preserved from ______by bacterial ______

· ______and ______can grow between pH 5 and 6

Osmotic Pressure

· Microbes dependent on ______to carry nutrients

o Microbes live in ______environments

· ______environments causes water to ______cell

o Growth inhibited due to ______

· Food preserved by high osmotic pressure - add ______

· ______tolerate high osmotic pressure

· Extreme halophiles ______ high salt conditions

o Live in the Dead Sea, salt lakes

Chemical Requirements

· Carbon

o Structural organic molecule, ______source

o ______use organic carbon sources

o ______use CO2

· Nitrogen

o In ______, proteins, ______

o Most bacteria decompose ______

o Some bacteria use ______or ______

o A few bacteria use ______from atmosphere

§ Called ______

· Sulfur

o In ______, thiamine, and biotin

o Most bacteria decompose ______

o Some bacteria use ______or ______

· Phosphorous

o In ______, RNA, ATP, and ______

o ______is a source of phosphorous

· Trace elements

o ______elements required in ______amounts

o Usually as ______

· Organic growth factors

o Organic compounds obtained ______

o Vitamins, amino acids, ______, ______

Oxygen

· ______metabolism provides more energy than ______metabolism

· BUT, Oxygen is ______in high amounts to ALL organisms

o ______forms of oxygen are highly reactive; ______cell components

o Many metabolic pathways exist to ______

· Singlet oxygen, 1O2- -

· Superoxide free radicals, O2-

o ______enzyme neutralizes free radicals

· Peroxide anion, O22-

o Neutralized by ______and ______enzymes

· Hydroxyl radicals, OH- -

· Obligate aerobes

o Grow where ______occurs

o Have ______that ______O2

· Facultative anaerobes

o Grow ______with ______

o ______growth via ______or ______

· Obligate anaerobes

o ______to detoxify ______

o Grow ______than ______

· Aerotolerant anaerobes

o Obligate ______, produce ______that inhibit competition from ______

o Possess enzymes to ______

· Microaerophiles

o ______detoxify high concentrations of ______

Biofilms

· ______that holds ______of bacteria together

o Share ______

o Sheltered from ______

· ______is a ______created by an extracellular polysaccharide

· Formed by ______ species in mouth

o Only when ______is present

· Plaque allows other microbes to ______

o Form ______that lead to tooth decay, gum disease

· Biofilms often form on ______and other tubing

· Numbers are often too low to detect

o Biofilm protects bacteria from ______

· Can grow rapidly once inside body, causing ______and other infections

Growing Microbes in the Lab

· ______: ______prepared for microbial ______

· ______: no ______microbes

· ______: ______of microbes (the ______) into sterile medium

· ______: microbes growing in/on culture medium

Agar

· Complex ______

· Used as ______for culture media in Petri plates, slants, and deeps

· Generally not ______by microbes

· Liquefies at 100°C

· Solidifies at ~40°C

Culture Media

· Chemically defined media: exact chemical composition ______

· Complex media: extracts and digests of yeasts, meat, or plants

o ______of nutrients

Biosafety Levels

· BSL-1: ______precautions

· BSL-2: ______, gloves, eye ______

· BSL-3: ______cabinets to prevent ______

· BSL-4: sealed, ______pressure

o ______is ______twice

The Growth of Bacterial Cultures

· Recall, microbial growth is increase in ______

· Bacteria reproduce by ______

o A single ______splits into ______cells

· Some microbes reproduce by ______

o Small growth (______) gets larger, and ______

· Generation time, _____ – the time it takes for a ______

o Essentially, time it takes for ______

· Varies among species

o Can be 20 mins, can be 20 days

· Microbes can grow ______in ideal conditions

o Eg, if g = ______, then:

§ 1 cell à 1 ______in _____ generations, ______

· Bacterial growth plotted on ______

o Numbers ______for linear or arithmetic graph

· ______scale increases in increments of ______

o 10, 100, 1,000, 10,000, etc …

· Converts rapidly increasing exponential growth from ______line into ______line

Phases of growth

· Bacteria growing in liquid have characteristic growth pattern

o When plotted on logarithmic graph – ______

· The Lag Phase

· The Log Phase

· The Stationary Phase

· The Death Phase

Measurements of Bacterial Growth

· Bacterial cultures are quantified by two general types of measurements

o ______measurements – measure ______

o Indirect Measurements – use ______measures to determine population size

Direct measurement of microbial growth

Standard Plate Counts

· Growth microbial sample on ______

o Count ______

o 1 ______= 1 ______

· Advantages

o Only ______counted

o Obtain ______

· Disadvantage

o Takes ______for colonies to form

o ______intensive

Filtration

· ______is passed through ______

o ______retained on ______

· ______is transferred to ______

· Useful when ______of bacteria in sample ______

· Often used to detect bacterial contamination of ______

Most probable number (MPN) method

· ______tube MPN test

· ______sample

o Count tubes with ______

· Useful when bacteria ______

· But, numbers are ______

o ____% accurate

Direct microscopic count

· Numbers of microbes counted ______

· ______results, but …

o ______difficult to count

o ______cells look like ______cells

o Need ______to count accurately

Indirect measurement of microbial growth

Turbidity

· ______, or ______, of a liquid culture

o Detected using a ______

· Higher ______, increased ______

· ______and ______method of obtaining quantity, but ….

o Do not obtain ______- values are only meaningful when ______to each other

o ______cells contribute to ______just like ______cells

Metabolic activity

· Assumes ______of bacteria produces ______or metabolic product

o Eg, measure ______build up

· Can be useful when cells ______

· Can be performed ______without needing to ______microbes

Dry weight

· Removal of microbes from growth medium, ______

· Useful for ______