bacterial growth &...
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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