7.2 Bacteria Key Concepts: How do the cells of bacteria differ from those of eukaryotes? What do bacteria need to survive? Under what conditions do bacteria thrive and reproduce? What positive roles do bacteira play in people’s lives? Key terms: Bacteria, flagellum, binary fission, asexual reproduction, sexual reproduction, conjugation, endospore, pasteurization, decomposer

Bacterial Cell Anton van Leeuwenhoek found cells by accident. He liked microscopes and was lookin’ at stuff. He thought they looked like monks’ chambers so he called them cells. He also saw some tiny worm like stuff but he didn’t know what they were Now we know they were bacteria (prokaryotes. Their genetic material is not contained in a nucleus)

Cell structure Cell structures Most bacterial cells lack mitochondria and golgi bodies. They are surrounded (like plant cells) by a rigid cell wall. Just inside the cell wall is the cell membrane. They also have cytoplasm and ribosomes and genetic material (which looks like a string) Flagellum – long whiplike structure that helps a cell move. It spins in place like a propeller. They may have one or more. Not all bacteria have flagella.

Cell sizes Bacteria vary greatly in size The largest known bacterium is about as large as a period (.), but the average is much smaller than that (usually a micrometer or 1 millionth of a meter in size)

Cell shapes Most are of 3 basic shapes: spherical, rodlike, or spiral. The chemical makeup of the cell wall determines shape

Obtaining food and energy Some bacteria are autotrophs They make food by using the sun’s energy OR chemicals they find around Some bacteria are heterotrophs They consume other organisms or the food that other organisms make

Respiration Energy comes from breaking down food in the process of respiration. Some need oxygen, some don’t.

Reproduction When bacteria have plenty of food, the right temperature, and other suitable conditions, they thrive and reproduce frequently.

Asexual reproduction Bacteria reproduce by binary fission – one cell divides to form two identical cells First a cell duplicates its genetic material then it divides it into new identical separate cells Asexual reproduction – involves only one parents and produces offspring that are identical to the parent.

Sexual reproduction Sexual reproduction- some bacteria “do it” Parents combine their genetic material to produce a new organism which differs from both parents Conjugation – one bacterium transfers from genetic material to another bacterium through a threadlike bridge. After the transfer, they separate. It results in bacteria with a new combination of genetic material . This passes to the offspring. It DOES NOT increase the number of bacteria, but it DOES result in genetically different bacteria.

Endospore formation An endospore is a small, rounded, thick-walled resting cell that forms inside a bacterial cell. It contains the cell’s genetic material and some of its cytoplasm. They help bacteria survive harsh conditions b/c they can resist freezing, heating, and drying. They are also light – so a breeze can carry one to new places, then it opens up and the bacterium grows and multiplies.

The role of bacteria in nature Bacteria are involved in oxygen and food production, also in health and medicine Oxygen: autotrophic (self-feeder) bacteria use the sun’s energy to release oxygen into the air Food: yogurt, apple cider, cheeses all use bacteria

Pasteurization Food is heated to the point where the temp is high enough to KILL bacteria muahahahahahaaaaaa

Environmental recycling Decomposers – organisms that break down large chemicals in dead organisms into small chemicals They are “nature’s recyclers” Some are “nitrogen fixing” – live in the soil and convert nitrogen gas into stuff plants need Environmental clean-up: Some bacteria eat oil and other nasty stuff

Health bidness Bacteria are all up in your bidness. They keep your digestive system healthy, for example. They also make vitamins that you need. Insulin – can be made by genetically engineered bacteria for people with diabeetus (diabetes).