Bacterial Bacterial Growth & Growth & ReproductionReproduction

Types of ReproductionTypes of Reproduction

AsexualAsexual

SexualSexual

Spore FormationSpore Formation

Asexual ReproductionAsexual Reproductiona.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 Reproductiona.k.a. a.k.a. ConjugationConjugation

PiliPili form bridge between different form bridge between different bacteriabacteria

Genetic material is transferredGenetic material is transferred

Genetic diversity RESULTSGenetic diversity RESULTS

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

Conjugation

Figure 8.25Bacterial 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 Why is sexual reproductionsexual reproduction of of bacteria bad for Humans?bacteria bad for Humans?Bacteria can pass on resistance Bacteria can pass on resistance to antibiotics , even between to antibiotics , even between species!!!!!!species!!!!!!

Spore FormationSpore FormationEndosporesEndospores

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 That Environmental Factors That Influence GrowthInfluence Growth

TemperatureTemperatureMost pathogens grow between 41Most pathogens grow between 41--140 140 ooFF (20(20--50 50 ooCC))

OxygenOxygenSome require OSome require O2 2 and others do notand others do not

pHpHMost bacteria grow in a range of pH 6.5Most bacteria grow in a range of pH 6.5--7.57.5Few can survive below ~pH 4Few can survive below ~pH 4Serious food contamination @ pH above ~5Serious food contamination @ pH above ~5

Water AvailabilityWater AvailabilityBacteria 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 Secretion of enzymes to ““eateat”” host host

tissuetissue

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

cellscells

Controlling GrowthControlling Growth & Prevention from Infection& Prevention from InfectionSterilizationSterilization = destruction/removal of all = destruction/removal of all microorganisms (including microorganisms (including endosporesendospores))

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

MilkMilk

Controlling Growth &Controlling Growth & Prevention from InfectionPrevention from InfectionSanitizationSanitization = microbes removed to a safe = microbes removed to a safe public health standard/levelpublic health standard/level

RestaurantsRestaurants

PreservationPreservation = process to delay spoilage of = process to delay spoilage of consumable goodsconsumable goods

CheeseCheese

Controlling GrowthControlling Growth & Prevention from Infection& Prevention from InfectionAntibioticsAntibiotics = 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 fungusfungusSome are used to control bacterial growth in the Some are used to control bacterial growth in the bodybodyOthers are put into foods to inhibit growth of Others are put into foods to inhibit growth of food spoiling bacteriafood spoiling bacteria