morphological characteristics ppt.pptx importance

Morphology of fungi

1. Cells are the fundamental units of living things, from the smallest bacterium to the largest of the plants and animals I ) Bacterial Morphology Bacteria, the smallest cells, are visible only with the aid of a microscope. The smallest bacteria ( Chlamydia  and  Rickettsia ) are only 0.1 to 0.2 um in diameter, whereas larger bacteria may be many microns in length Most species, however, are approximately 1 um in diameter and are therefore visible using the light microscope, which has a resolution of 0.2 um. In comparison, animal and plant cells are much larger, ranging from 7 um (the diameter of a red blood cell) to several feet (the length of certain nerve cells). 

2. Major Characteristics of Eukaryotes and Prokaryotes    Characteristic    Eukaryote    Prokaryote       Major Groups    Algae, fungi, protozoa, plants, animals.    Bacteria.       Size (approximate)    >5 um.    0.5 to 3 um.       Nuclear Structures              - Nucleus    Classic membrane.    No nuclear membrane.          - Chromosomes    Strands of DNA; diploid genome.    One circular DNA; haploid genome.        Cytoplasmic Structures              - Mitochondria    Present.    Absent.          - Golgi Bodies    Present.    Absent.          - Endoplasmic Reticulum    Present.    Absent.          - Ribosomes    80S (60S + 40S).    70S (50S + 30S).          - Cytoplasmic Membrane    Contains sterols.    Does not contain sterols.       Cell Wall    Absent of composed of chitin.    Complex structure.       Reproduction    Sexual and asexual.    Asexual (binary fission).       Movement    Complex flagellum, if present.    Simple flagellum, if present.       Respiration    Via mitochondria.    Via cytoplasmic membrane.

3. II) Differences Among Prokaryotes       Bacteria can be distinguished from one another by their morphology (size, shape, and staining characteristics) and metabolic, antigenic, and genetic characteristics. Although bacteria are difficult to differentiate by size, they do have different shapes. A spherical bacterium, such as  Staphylococcus , is a coccus . A rod-shaped bacterium, such as  Escherichia coli , is a bacillus. And the snakelike treponeme is a spirillum . In addition,  Nocardia  and  Actinomyces  species have branched filamentous appearances similar to those of fungi. . 

4. Some bacteria form aggregates such as the grapelike clusters of  Staphylococcus aureus  or the diplococcus (two cells together) observed in  Streptococcus  or  Neisseria  species The Gram stain is a powerful, easy test that allows clinicians to distinguish between the two major classes of bacteria . Bacteria that are heat-fixed or otherwise dried onto a slide are stained with crystal violet. T his stain is precipitated with Gram iodine, and then the unbound and excess stain is removed by washing with the acetone-based decolorizer . A counterstain , safranin , is added to stain any decolorized cells red. This process takes less than 10 minutes. 

5. III) Comparison of the Gram positive and Gram negative bacterial cell walls. A, a Gram positive bacterium has a thick peptidoglycan layer that contains teichoic and lipoteichoic acids. B, a Gram negative bacterium has a thin peptidoglycan layer and an outer membrane that contains lipopolysaccharide , phospholipids, and proteins. The periplasmic space between the cytoplasmic and outer membranes contains transport, degradative , and cell wasll synthetic proteins. The outer membrane is joined to the cytoplasmic membrane at adhesion points and is attached to the peptidoglycan by lipoprotein links

6. IV ) Gram stain morphology of bacteria. A, the crystal violet Gram stain is precipitated by Gram iodine and is trapped in the thick peptidoglycan layer in Gram positive bacteria. The decolorizer disperses the Gram negative outer membrane and washes the crystal violet from the thin layer of peptidoglycan . Gram negative bacteria are visualized by the red counterstain . B, bacterial morphologies        For Gram positive bacteria, which turn purple, the stain gets trapped in a thick, cross-linked, meshlike structure, the peptidoglycan layer, which surrounds the cell. Gram negative bacteria have a thin peptidoglycan layer that does not retain crystal violet stain, so the cells must be counterstained with safranin and turned red.  Bacteria that cannot be classified by Grain stain include mycobacteria , which have a waxy outer shell and are distinguished with the acid-fast stain.

7. Bacterial cell shape is determined primarily by a protein called MreB . MreB  forms a spiral band – a simple cytoskeleton – around the interior of the cell just under the cytoplasmic membrane.  It is thought to define shape by recruiting additional protens that then direct the specific pattern of bacterial cell growth. For example, bacillus-shaped bacteria that have an inactivated MreB gene become coccoid shaped, and coccus -shaped bacteria naturally lack the MreB gene. Most bacteria come in one of three basic shapes:  coccus , rod or bacillus, and spiral. . The coccus   (def) The cocci are spherical or oval bacteria having one of several distinct  arrangements  based on their planes of division. a. Division in one plane produces either a  diplococcus  or streptococcus arrangement.

8. A) diplococcus : cocci arranged in pairs streptococcus: cocci arranged in chains b. Division in  two planes  produces a  tetrad  arrangement. a tetrad: cocci arranged in squares of 4 c. Division in  three planes  produces a  sarcina   arrangemen sarcina : cocci in arranged cubes of 8

9. EX: Scanning Electron Micrograph of  Streptococcus pneumoniae

10. B) gram-positive (purple) cocci in chains   streptococcus: cocci arranged in chains

11. EX: Electron Micrograph of  Streptococcus pyogenes   , a Streptococcus

12. Division in two planes produces a tetrad arrangement.

13. c. Division in three planes produces a  sarcina  arrangement. sarcina : cocci in arranged cubes of 8

14. d. Division in random planes produces a staphylococcus arrangement. staphylococcus: cocci arranged in irregular, often grape-like clusters - photomicrograph of a  staphylococcus   Gram Stain of  Staphylococcus aureus

15. Staphylococcus aureus Negative Image cocci in irregular clusters.

16. V) Bacteria grow tremendously fast when supplied with an abundance of nutrients. Different types of bacteria will produce different-looking colonies, some colonies may be colored, some colonies are circular in shape, and others are irregular. The characteristics of a colony (shape, size, pigmentation, etc.) are termed the colony morphology. Colony morphology is a way scientists can identify bacteria. In fact there is a book called Bergey's Manual of Determinative Bacteriology (commonly termed Bergey's Manual) that describes the majority of bacterial species identified by scientists so far. This manual provides descriptions for the colony morphologies of each bacterial species.

17. Although bacterial and fungi colonies have many characteristics and some can be rare, there are a few basic elements that you can identify for all colonies: Form - What is the basic shape of the colony? For example, circular, filamentous, etc. Elevation - What is the cross sectional shape of the colony? Turn the Petri dish on end. Margin - What is the magnified shape of the edge of the colony? Surface - How does the surface of the colony appear? For example, smooth, glistening, rough, dull (opposite of glistening), rugose (wrinkled), etc.

18. Opacity - For example, transparent (clear), opaque, translucent (almost clear, but distorted vision, like looking through frosted glass), iridescent (changing colors in reflected light), etc. Chromogenesis (pigmentation) - For example, white, buff, red, purple, etc. Please note that 3 additional elements of morphology should be examined only in a supervised laboratory setting: consistency, emulsifiability , and odor. Refer to the diagram below for illustrated examples of form, elevation, and margin: (2)

19. VI) What Can Grow on a Nutrient Agar Plate? - Bacteria: Each distinct circular colony should represent an individual bacterial cell or group that has divided repeatedly. Being kept in one place, the resulting cells have accumulated to form a visible patch. Most bacterial colonies appear white, cream, or yellow in color, and fairly circular in shape. For example:

20. Bacillus subtilis . Staphylococcus aures

21. Streptococcus pyogenes - Yeasts: Yeast colonies generally look similar to bacterial colonies. Some species, such as  Candida , can grow as white patches with a glossy surface.

22. Round yeast colonies Pink yeast colonies

23. - Molds: Molds are actually fungi, and they often appear whitish grey, with fuzzy edges. They usually turn into a different color, from the center outwards. Two examples of molds are shown below: Black Mold ( Aspergillus nidulaus ) Green Mold ( Trichoderma harzianum )

24. Other Fungi: Moss green colonies, a white cloud, or a ring of spores can be attributed to the growth of  Aspergillus , which is common in such fungal infections as athlete's foot. Here is an example of what Aspergillus  looks like: (12)

25. Scanning electron micrograph of  Escherichia coli