Lecture 1; Bacterial Classification and Morphology Morphology is the study of organistic structure Physiological: the study of a function of an organism - Criteria for Classification:  Macroscopic (can see w/naked eye) - colony morphology Microscopic (need microscope) - cell shape, staining properties, etc. Physiological - presence/absence of particular enzymes Chemical Analysis- not used so much. Decomposes bacteria, puts in blender to find what substances make it up.  Serological - use of antibodies Genetic - G+C, rRNA, chromosome/gene sequence- Morphology of Bacterial Cells  Most common cell shapes : coccus (cocci) – spherical (perfect spheres) bacillus (bacilli) – rod (perfect rods) Also – coccobacillus (short rod), vibrio (short curved rod), spirillium (spiral rod),(these have morphologies/shapes and look similar) pleomorphic (variable shape) (each cell look different) , etc…- Pathology Relationship to pathology - ask yourself, would you rather beinfected with a bacterium (virus) with a particular characteristic or without??? Strictly speaking, bacterial cell shape does not correlate withpathology.- Grouping of Bacterial Cells  Bacterial cells divide by a process known as binary fission which is a more simple process than Mitosis (more on this later). Some bacterial cells remain loosely attached following nuclear fission (cell division) forming arrangements characteristic of their genus and species. This occurs more often in cocci than in bacilli. Prokaryotic cells (bacteria) reproduce primarily by binary fission Binary fission: a simple process of cells splitting equally into two. (Some bacteria are surrounded by an extracellular layer called a “sheath”. This sheath also holds bacterial cells together after cell division) Long Chains- filamentous groupings of 2- diplococci any coccus that forms big clumps is staphylococcus- Grouping AND Pathology (both good news and bad news) An organism that forms groups :Spreads more slowly (good news)Can hide from the Immune System longer (bad news - explain) (delays immune responses) - Bacterial Cell Structure Flagella - allow bacteria to move from one place to another (bacterial propellers).  Flagella: Flagella- provide the power of motility. This allows cells to swim freely through an aqueous habitat. Under a microscope they display three distinct parts: - the filament- helical structure composed of a protein called falgellin. – thehook is anchored to the cell by the basal body- a stack of rings firmly anchored through the cell wall to the cell membrane.o monotrichous (single)o lophotrichous (bunches/tufts) (groups)o amphitrichous (both poles) (at either end) o peritrichous (all over surface) Flagella vary both in number and arrangement according to 2 patterns. 1) in a polar arrangement, the flagella are attached at one orboth ends of a cell. 3 subtypes are - monotrichous- with a single flagellum- lophotricphous- with small bunches or tufts of flagella emerging from the same site- amphitrichous- with flagella at both poles of the cell. 2) peritrichious arrangement flagella are dispersed randomlyover the surface of the cell.  Flagella can detect and move in response to chemical signals- a type of behavior called chemotaxis - positive chemotaxis is movement of a cell in the direction of a favorable chemical stimulus (usually a nutrient)- negative chemotaxis is movement awayfrom a repellent (potentially harmful) compound.  Flagella can guide bacteria in a certain direction b/c the system for detecting chemicals is linked to the mechanisms that drive the flagellum.  Taxis: the capabili to move toward or away from a stimulus Chemotaxis: directional movement. toward/away from chemical stimuli ex: toward food and oxygen and away from stimuli such as chemical toxins Magnetotaxis: north and south and up and down. Often live in aquatic sentiments and find that too much oxygen can be toxic. Direct their rotating flagella to carry them into deeper layers of sentiments for deeper nutrients they require.  Located in the cell membrance are clusters of receptors that bind specific molecules coming from the immediate environment. The attachement of sufficient numbers of these molecules transmits signals to the flagellum and setsit into rotary motion. If several flagellum are present, they become aligned and rotate as a group. As a flagellum roatates counterclockwise, the cell itself swims in a smooth linear direction toward the stimulus. This action is call run. Runs are interrupted as various intervals by tumbles caused by the flagellum reversing its direction. This makes the cell stop and change its course. It is believed that attractant molecules inhibit tumbles, increase runs, and permit progress toward stimulus. Repellents cause numerous tumbles. Allowing the bacterium to redirect itself away from the stimulus. Some photosynthetc bacteria exhibit phototaxis, a type of movement in response to light rather than chemicals. - Other Appendages :  Fimbrae and Pili both refer to bacterial surface appendages that are involved in interactions with other cells but do not provide locomotion.  Fimbrae- small, bristlelike fibers emerging from the surface of many bacterial cells. Their exact composition varies, butmost of them contain protein. Fimbrae have an inherent tendency to stick to each other and to surfaces. They maybe responsible for the mutual clinging of cells that leads to biofilms and other thick aggregates of cells on the surface of liquids and for the microbial colonization of inanimate solids such as rocks and glass. Some pathogens can colonize and infect host tissues because of tight adhesion between their fimbrae and epithelial cells. EX: gonoccus- agent of gonorrhea conlonizes the genitourinary tract and E. Coli colonizes the intestine by this means.  Pili- a pilus is an elongated, rigid tubular stucture made of speical protein, pilin. True pili have been found only on gram-negative bacteria where they are utilized in “mating” process between cells called conjugations- which involves partial transfer of DNA from one cell to another. A pilus froma donor cells unites with a recipent cell, thereby providing a cytoplasmic connection for making the transfer. - Glycocalyx  Slime layer - A loose gel-like layer usually composed of polysaccharide that functions to protect from water and nutrient loss and in adhesion –