Bacterial G & R (Growth and Reproduction)

Types  Asexual  Sexual  Spore Formation

Asexual Reproduction  a.k.a. Binary Fission  Bacteria reproduce by splitting in two  NO genetic diversity  Rapid massive reproduction possible

Binary Fission

Sexual Reproduction  a.k.a. Conjugation  Pili form bridge between different bacteria  Genetic material is transferred  Genetic diversity RESULTS  Allows bacteria to transfer immunity to antibiotics to other species (contained 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 are much closer together. Notice that one cell has numerous fimbriae.

QUESTION??  Why is this bad for Humans?

Spore Formation  Endospores  Formed under conditions of environmental stress  Spores are thick walled & contain genetic information  Extremely resistant to heat, desiccation (drought), cold, UV light, and toxic chemicals

Spore Formation  Spores that survive such conditions go on to become typical cells  By being exposed to heat or chemicals = the spore takes on water, swells, and releases a vegetative (metabolically active/growing) cell

Sporulation

Nutrient & Energy Sources for Bacterial Growth  Organic matter  Carbon (from CO 2 )  Sunlight  Chemicals

Environmental Factors That Influence Growth Temperature Temperature Most pathogens grow between o F (20-50 o C) Most pathogens grow between o F (20-50 o C) Oxygen Oxygen Some require O 2 and others do not Some require O 2 and others do not pH pH Most bacteria grow in a range of pH Most bacteria grow in a range of pH Few can survive below ~pH 4 Few can survive below ~pH 4 Serious food pH above ~5 Serious food pH above ~5 Water Avaliability Water Avaliability Bacteria need moisture Bacteria need moisture

Limits to Growth pH <4.6 (acidic) HOT and DRY environment NO FOOD source NO SPACE for growth

How Do Bacteria Cause Disease? 1. Metabolize Host –Secretion of enzymes to “eat” host tissue 2. Produce Toxins –Bacterial waste can be toxic to host cells

Controlling Growth/ Tx & Prevention from Infection Sterilization = destruction/removal of all microorganisms (including endospores) Sterilization = destruction/removal of all microorganisms (including endospores) Used for surgical instruments Used for surgical instruments Disinfection = removal of most (the harmful) microbes Disinfection = removal of most (the harmful) microbes Lysol wipes, etc. Lysol wipes, etc. Pasteurization = mild heat treatment to rid consumables of spoilage microorganisms (not sterile) Pasteurization = mild heat treatment to rid consumables of spoilage microorganisms (not sterile) Milk Milk

Controlling Growth/ Tx & Prevention from Infection Sanitization = microbes removed to a safe public health standard/level Sanitization = microbes removed to a safe public health standard/level Restaurants Restaurants Preservation = process to delay spoilage of consumable goods Preservation = process to delay spoilage of consumable goods Cheese Cheese

Controlling Growth/ Tx & Prevention from Infection Antibiotics = a substance produced by microorganisms that in small amounts inhibits another microorganism Antibiotics = a substance produced by microorganisms that in small amounts inhibits another microorganism Usually produced naturally by a bacteria or fungus Usually produced naturally by a bacteria or fungus Some are used to control bacterial growth in the body Some are used to control bacterial growth in the body Others are put into foods to inhibit growth of food spoiling bacteria Others are put into foods to inhibit growth of food spoiling bacteria