Bacterial G & RBacterial G & R(Growth and Reproduction) (Growth and Reproduction)

TypesTypes AsexualAsexual

SexualSexual

Spore FormationSpore Formation

Asexual ReproductionAsexual Reproduction a.k.a. a.k.a. Binary FissionBinary Fission

Bacteria reproduce by splitting in twoBacteria reproduce by splitting in two

NO genetic diversityNO genetic diversity

Rapid massive reproduction possibleRapid massive reproduction possible

Binary Fission

Sexual ReproductionSexual Reproduction a.k.a. a.k.a. ConjugationConjugation

Pili form bridge between different Pili form bridge between different bacteriabacteria

Genetic material is transferredGenetic material is transferred

Genetic diversity RESULTSGenetic diversity RESULTS

Allows bacteria to transfer immunity to Allows bacteria to transfer immunity to antibiotics to other species (contained antibiotics to other species (contained in genes)in genes)

Conjugation

Figure 8.25 Bacterial conjugation. The sex pilus connecting these cells undergoing conjugation allows the transfer of genetic information. At the actual time of genetic exchange, the cells’ connecting bridge contracts and the cells aremuch closer together. Notice that one cell hasnumerous fimbriae.

QUESTION??QUESTION?? Why is this bad for Humans?Why is this bad for Humans?

Spore FormationSpore Formation EndosporesEndospores

Formed under conditions of environmental Formed under conditions of environmental stressstress

Spores are thick walled & contain genetic Spores are thick walled & contain genetic informationinformation

Extremely resistant to heat, desiccation Extremely resistant to heat, desiccation (drought), cold, UV light, and toxic chemicals(drought), cold, UV light, and toxic chemicals

Spore FormationSpore Formation

Spores that survive such conditions Spores that survive such conditions go on to become typical cellsgo on to become typical cells

By being exposed to heat or chemicals = By being exposed to heat or chemicals = the spore takes on water, swells, and the spore takes on water, swells, and releases a vegetative (metabolically releases a vegetative (metabolically active/growing) cellactive/growing) cell

SporulationSporulation

Nutrient & Energy Sources for Bacterial Growth

Organic matter

Carbon (from CO2)

Sunlight

Chemicals

Environmental Factors Environmental Factors That Influence GrowthThat Influence Growth

TemperatureTemperature Most pathogens grow between 41-140 Most pathogens grow between 41-140 ooF (20-F (20-

50 50 ooC)C) OxygenOxygen

Some require OSome require O2 2 and others do notand others do not pHpH

Most bacteria grow in a range of pH 6.5-7.5Most bacteria grow in a range of pH 6.5-7.5 Few can survive below ~pH 4Few can survive below ~pH 4 Serious food contamination @ pH above ~5Serious food contamination @ pH above ~5

Water AvaliabilityWater Avaliability Bacteria need moistureBacteria need moisture

Limits to Growth• pH <4.6 (acidic)

• HOT and DRY environment

• NO FOOD source

• NO SPACE for growth

How Do Bacteria Cause How Do Bacteria Cause Disease?Disease?

1.1. Metabolize HostMetabolize Host– Secretion of enzymes to “eat” host Secretion of enzymes to “eat” host

tissuetissue

2.2. Produce ToxinsProduce Toxins– Bacterial waste can be toxic to host Bacterial waste can be toxic to host

cellscells

Controlling Growth/Controlling Growth/Tx & Prevention from Tx & Prevention from

InfectionInfection SterilizationSterilization = destruction/removal of all = destruction/removal of all microorganisms (including endospores)microorganisms (including endospores) Used for surgical instrumentsUsed for surgical instruments

DisinfectionDisinfection = removal of most = removal of most (the harmful) microbes(the harmful) microbes Lysol wipes, etc.Lysol wipes, etc.

PasteurizationPasteurization = mild heat treatment to = mild heat treatment to rid consumables of spoilage rid consumables of spoilage microorganisms (not sterile)microorganisms (not sterile) MilkMilk

Controlling Growth/Controlling Growth/Tx & Prevention from Tx & Prevention from

InfectionInfection SanitizationSanitization = microbes removed to a = microbes removed to a

safe public health standard/levelsafe public health standard/level RestaurantsRestaurants

PreservationPreservation = process to delay = process to delay spoilage of consumable goodsspoilage of consumable goods CheeseCheese

Controlling Growth/Controlling Growth/Tx & Prevention from Tx & Prevention from

InfectionInfection AntibioticsAntibiotics = a substance produced by = a substance produced by

microorganisms that in small amounts microorganisms that in small amounts inhibits another microorganisminhibits another microorganism Usually produced naturally by a bacteria or Usually produced naturally by a bacteria or

fungusfungus Some are used to control bacterial growth Some are used to control bacterial growth

in the bodyin the body Others are put into foods to inhibit growth Others are put into foods to inhibit growth

of food spoiling bacteriaof food spoiling bacteria