Kingdom Monera Bacteria Structure, Shape, Movement & Reproduction

Common Characteristics Bacteria are prokaryotic cells They are 1-10 um in length (much smaller than eukaryotic cells) Except for ribosomes, there are no cytoplasmic organelles Lack a defined nucleus Most have a cell wall, cell wall may be surrounded by a capsule May have a flagella for movement

Typical Prokaryotic Cell

Bacteria Shapes Bacteria are commonly in three basic shapes Coccus (sphere) Bacillus (rod) Spirillium (spiral)

Cell Wall Characteristics Different types of bacteria have different types of cell walls Differences in cell wall composition can be studied using gram staining Depending on their cell wall, bacteria can be classified as Gram-Positive or Gram Negative

Gram Positive Bacteria These bacteria have a thick layer of peptidoglycan in their cell walls These bacteria retain dye-iodine complex in their cell walls and appear purple under the microscope

Gram Negative Bacteria These bacteria have a thin layer of peptidoglycan in their cell walls These bacteria do NOT retain the dye These bacteria appear pink under the microscope

Bacterial Movement Flagella Long whip like structure that propels bacteria May have none, one or several

Bacterial Movement Pilli (cilia) Short hair like appendages that adhere bacteria to different surfaces

Bacterial Movement Slime Some bacteria secrete slime like material they glide along No Movement Some bacteria do not movement all

Bacterial Reproduction In favorable conditions, bacteria can grow and reproduce as often as every 20 minutes Methods of Bacterial Reproduction Binary Fission Conjugation Spore Formation

Binary Fission Asexual form of reproduction There is no exchange or recombination of genetic material How? When a bacterial cell has grown to double its original size, it replicates its DNA and divides in half to produce two identical daughter cells

Binary Fission

Conjugation A form of sexual reproduction An exchange of genetic material is involved When 2 cells conjugate, a long protein bridge is formed between them Genetic info is transferred from one cell to the other via this bridge The recipient now has new genetic material & the genetic diversity in the population has increased This helps the bacteria survive environmental changes

Conjugation

Spore Formation Not really a form of reproduction but enables the bacteria to survive In unfavorable conditions, bacteria can form endospores The endospores stay dormant until conditions are favorable again When conditions are favorable, the endospore will release the bacterial cell

Spore Formation