Advanced Biology: Bacteria Basics Mrs. Kromko Honesdale High School Rm 103

Pathogenic vs. Non-pathogenic Pathogenic bacteria – bacteria capable of causing disease in their host. Examples include: MRSA (Methicillin-Resistance Staphylococcus aureus) Mycobacterium tuberculosis Non-pathogenic bacteria – bacteria that do NOT cause disease in their host. Lactobacillus acidophilus Streptococcus thermophilus

Bacterial shapes and arrangements Average size: 0.5 - 2 µm in diameter Three basic shapes: Coccus: spherical (Cocci – pl) Bacillus: rod-shaped (Bacilli – pl) Spirillum: spiral-shaped (Spirilli – pl) Vibrio – comma shaped Spirochete – corkscrew Many arrangements: Diplo – 2 4. Tetra- 4 Strepto – chains 5. Sarcinae – 8 Staphylo - clusters Filaments – rod shaped bacteria that DON’T divide, but continue to grow.

Motility 1.) True Motility – movement in a consistent direction or path Flagella – long, whip-like appendages made of proteins Monotrichous – single flagella located at one end Amphitrichous – flagella located at both ends Lophotrichous – two or more flagella located at one or both ends Peritrichous – flagella located all over the bacterium Cilia – short, oar-like appendages 2.) Brownian Movement – movement caused by molecules of the suspending liquid (often water) colliding with the organism.

Types of Movement Bacilli – most move by means of flagella Spirilli – move by means of flagella or helical undulation (thrashing) Cocci – most are not motile; however some can glide

Microbial reproduction Asexual Reproduction – reproduction involving one parent Ex) Binary Fission: one parent cell replicates its DNA and divides to form two new cells (bacteria) Ex) Budding: daughter cell grows a new, small cell from the surface of the parent cell (yeast) Ex) Mitosis: division of the nucleus of eukaryotic cells that allows for the production of daughter cells (many protists) Sexual Reproduction – reproduction involving two parents Ex) Meiosis: process that produces male and female sex cells (gametes). It can be used to produce spores in some fungi. Ex) Conjugation: not really a form of sexual reproduction; however an exchange of genetic material from one bacterial cell to another occurs (can lead to bacterial resistance)

Bacterial Cell Structure Cell Wall – Provides structure, shape and an anchorage point for flagella in bacterial cells Composition: The cell wall is made of peptidoglycan (disaccharides linked by polypeptides). The amount of peptidoglycan in the cell wall of bacteria is the basis for Gram staining. Cell Membrane – Forms a barrier between the extracellular space and intracellular space. It also serves as a regulatory structure controlling what enters and exits a cell. Composition: The cell (plasma) membrane is made of a phospholipid bilayer with proteins embedded in it to aid in the transport of molecules. Ribosomes – Location of protein synthesis (linking of amino acids to form proteins) Nucleiod Region – location of genetic material (DNA) free-floating in the cytoplasm; single circular chromosome Plasmids – small, circular pieces of DNA molecules that can reproduce independently of the main chromosome

Bacterial Cell Structure continued…. Inclusions – small structures suspended with the cytoplasm 1.) granules: cell structures not bound by membranes that store and carry substances that do not easily dissolve in the cytoplasm (ex. Glycogen) 2.) vesicles: cell structures used for gas regulation in some aquatic bacteria (different composition than vesicles found in eukaryotes.) Endospores – structures formed on the inside of bacterial cells to increase survival during adverse conditions (cold, heat, dehydration, radiation, pH fluctuations, etc…) Glycocalyx – A viscous, gelatinous layer outside the cell wall that is composed of polysaccharides. If firmly attached to the cell wall it is called a capsule. Not all bacteria have capsules. If the glycocalyx is loosely attached to the cell wall it is called the slime layer. A slime layer is thinner than a capsule and helps prevent drying and allow bacteria to adhere to other structures. Pilli- tiny hollow projections that are similar to flagella, but aid in attaching bacteria to surfaces instead of aiding in movement. Bacteria can have two types of pilli: 1.) conjugation pilli – allows for conjugation to occur 2.) attachment pilli (A.K.A. Fimbriae) –help bacteria adhere to surfaces Spore formers: In bacteria spores are associated with survival, NOT reproduction. Bacteria will form spores in preparation for adverse conditions. At the conclusion of adverse conditions, spores will germinate and develop into functioning cells.

Bacterial variation Bacterial variation – a change in the genotype (DNA) of a bacterium Causes: Mutations – Random changes in genetic sequence (DNA) Transformation – Naked DNA is integrated into bacterial DNA Conjugation – Plasmid is transferred from one bacteria to another Transduction – A virus picks ups bacterial DNA and integrates it into a new bacterial cell. Bacterial variations may cause antibiotic resistance.