Microbial World 2nd-Year Natural Sciences PDF

Chapter I. MICROBIAL WORLD 2nd-year Natural Sciences Dr. Fatima-Zohra Kenza LABBANI Natural Sciences Department [email protected] Part 4. EUKARYOTES Microscopic Algae and Protozoa Microscopic Alg...

Chapter I. MICROBIAL WORLD 2nd-year Natural Sciences Dr. Fatima-Zohra Kenza LABBANI Natural Sciences Department [email protected] Part 4. EUKARYOTES Microscopic Algae and Protozoa Microscopic Algae General Characteristics of Microscopic Algae Microscopic algae or Microalgae are predominantly unicellular eukaryotic organisms but can form colonies or filaments. They are typically found in freshwater and marine environments General Characteristics of Microscopic Algae They perform photosynthesis, converting (CO2) and (H2O) into organic compounds (such as sugars) and (O2), contributing to approximately 50% of the Earth's oxygen production General Characteristics of Microscopic Algae Microalgae contain various pigments, such as chlorophylls (usually chlorophyll a and b), carotenoids, and phycobiliproteins. These pigments enable light capture and give rise to their diverse colours General Characteristics of Microscopic Algae Microalgal cell walls are often composed of cellulose, silica in diatoms, or other polysaccharides General Characteristics of Microscopic Algae Microalgae exhibit different cell organisation forms, including: 1) Unicellular Forms: Many microalgae are single, independent cells that can be either motile (with flagella) or non-motile Examples: Chlorella, Chlamydomonas, Diatoms, and Dinoflagellates. General Characteristics of Microscopic Algae 2) Colonial Forms: Some microalgae form colonies, where multiple cells are grouped and held together by a shared extracellular matrix (ECM) or mucilage Examples: Scenedesmus (2-16 cells), Volvox (500 to 60,000 cells) General Characteristics of Microscopic Algae 3) Filament Forms: They form multicellular chains of cells called filaments. Filamentous growth results from repeated cell division in a single plane, forming long chains of cells connected end-to-end. Filaments can be simple and unbranched, like Spirogyra. General Characteristics of Microscopic Algae 3) Filament Forms: Or they may exhibit branching like Cladophora. Filamentous microalgae are common in both freshwater and marine environments Microscopic Fungi ▪ Reproduction Reproduction of Microscopic Algae Asexual reproduction: is the most common method of reproduction in microalgae, enabling rapid population growth under favourable conditions 1) Binary fission: The primary asexual reproduction method in unicellular microalgae, where a single algal cell divides into two daughter cells. This process is common in unicellular microalgae like Chlamydomonas. Reproduction of Microscopic Algae 2) Fragmentation: In multicellular filamentous algae, such as Spirogyra, the thallus (body) breaks into smaller fragments that grow into new organisms. Reproduction of Microscopic Algae 3) Spore formation: microalgae can reproduce via spores germinating into new individuals and producing either Zoospores (flagellated spores like in Chlamydomonas), or Aplanospores (Non-motile spores) Reproduction of Microscopic Algae Reproduction of Microscopic Algae Sexual reproduction: 1) Conjugation In this process, two filaments align side by side and a conjugation tube forms between adjacent cells. The contents of one cell (acting as a male) move through the tube to fuse with the contents of another cell (acting as a female), forming a zygote. The zygote undergoes meiosis to produce new haploid cells. Reproduction of Microscopic Algae Sexual reproduction: 2) Isogamy: Two morphologically identical gametes fuse. The resulting zygote develops into a new individual. 3) Anisogamy: The fusion of two morphologically different gametes (typically a larger "female" gamete and a smaller "male" gamete). The formation of a zygote that develops into a new individual Reproduction of Microscopic Algae Life cycle of Chlamydomonas Microscopic Fungi ▪ Classification Classification of Microalgae 1) Green Algae (Chlorophyta) Microalgae with chlorophyll a and b, giving them a green colour Similar photosynthetic pigments to land plants Cell walls primarily composed of cellulose Example: Chlorella, Chlamydomonas Classification of Microalgae 2) Red Algae (Rhodophyta) Contain chlorophyll a, phycobilins (phycoerythrin gives them a red colour). Mostly marine species and are used in the food industry for products like agar and carrageenan Cell walls are composed of cellulose and other polysaccharides, such as agar. Example: Porphyridium. Classification of Microalgae 3) Diatoms (Bacillariophyta) Cell wall made of silica (forming a glass-like structure called a frustule). Pigments: Chlorophyll a, c, and fucoxanthin (brownish pigment). Example: Thalassiosira and Phaeodactylum. Classification of Microalgae 4) Euglenoids (Euglenophyta) Pigments: Chlorophyll a, b. Storage product: Paramylon (carbohydrate similar to starch). No rigid cell wall; instead, they have a flexible pellicle made of protein strips. Example: Euglena Classification of Microalgae 5) Golden Algae (Chrysophyta) They contain chlorophyll a and c, as well as accessory pigments (like fucoxanthin, the dominant carotenoids), which gives them golden-brown pigmentation Primarily freshwater species Classification of Microalgae 6) Dinoflagellates (Dinophyta) Pigments: Chlorophyll a, c, peridinin (a carotenoid). Cell wall composed of cellulose plates called thecae. Example: Alexandrium and Ceratium. Protozoa  Protozoa are unicellular eukaryotic organisms that live in aqueous environments and soil. They are typically larger and more complex than bacteria, ranging from 10-50 μm in size, though some can reach up to 1 mm. They are heterotrophs, obtaining their nutrition by consuming other organisms or organic matter in their environment. General Characteristics of Protozoa ✓ Protozoa are unicellular eukaryotic organisms ✓ Heterotrophic nutrition, obtaining their nutrition by consuming other organisms or organic matter in their environment ✓ Motility through various structures like cilia, flagella, or pseudopodia ✓ Reproduction by binary fission, multiple fission, or sexual processes ✓ Form protective cysts in unfavourable conditions ✓ Free-living or parasitic lifestyles Protozoa ▪ Reproduction Reproduction of Protozoa Protozoa exhibit both asexual and sexual reproduction methods: Asexual reproduction: is the primary mode of reproduction for most protozoa, allowing for rapid population growth under favourable conditions ✓ Binary fission: The most common method, where the cell divides into two identical daughter cells ✓ Multiple fission: The nucleus divides multiple times before cytoplasmic division, producing numerous daughter cells Reproduction of Protozoa Sexual reproduction: involves the exchange or fusion of genetic material between two individuals, including conjugation Reproduction of Protozoa Sexual reproduction by Conjugation involves a temporary fusion of two cells (two individuals) to exchange genetic material  Conjugation in Paramecium involves a series of steps that facilitate genetic recombination without increasing the number of individuals. Two cells align and undergo meiosis of their micronuclei, resulting in one functional haploid micronucleus per cell. These haploid micronuclei undergo mitosis, and each cell exchanges one with its partner. The exchanged nuclei then fuse (syngamy), restoring the diploid state. The new diploid micronucleus divides to form both new micronuclei and macronuclei. After separation, each cell has a new set of nuclei, enhancing genetic diversity and adaptability through recombination Protozoa ▪ Classification Classification of Protozoa Protozoa are classified based on their locomotory structures and life cycles. The traditional classification system includes four main groups: ✓ Sarcodina (Rhizopoda) ✓ Mastigophora (Flagellata) ✓ Ciliophora (Ciliata) ✓ Sporozoa (Apicomplexa) Classification of Protozoa Sarcodina (Rhizopoda): Move using pseudopodia. Examples: Amoeba, Entamoeba Mastigophora (Flagellata): Possess one or more flagella. Examples: Trypanosoma, Giardia Ciliophora (Ciliata): Move using cilia. Examples: Paramecium Sporozoa (Apicomplexa): Lack of locomotory structures in the adult stage. Reproduce by spore formation. Examples: Plasmodium, Toxoplasma Classification of Protozoa Amoeba Classification of Protozoa Leishmania Trypanosoma Classification of Protozoa Classification of Protozoa Plasmodium  THE END Dr. Fatima-Zohra Kenza LABBANI [email protected] Natural Sciences Department