Microbial Cell Structure PDF

 Prokaryotes have a nucleoid (nuclear body) rather than an enveloped nucleus and lack membrane-bound cytoplasmic organelles. The plasma membrane in prokaryotes performs many of the functions carried out by membranous organelles in eukaryotes. Multiplication is by...

 Prokaryotes have a nucleoid (nuclear body) rather than an enveloped nucleus and lack membrane-bound cytoplasmic organelles. The plasma membrane in prokaryotes performs many of the functions carried out by membranous organelles in eukaryotes. Multiplication is by binary fission.  Eukaryotes are organisms whose cells contain a nucleus and other membrane-bound organelles. Eukaryotes may be either single-celled or multicellular.  Some species of bacteria have a third protective covering, a capsule made up of polysaccharides (complex carbohydrates). Capsules play a number of roles, but the most important are to keep the bacterium from drying out and to protect it from phagocytosis (engulfing) by larger microorganisms. The capsule is a major virulence factor in the major disease-causing bacteria, such as Escherichia coli and Streptococcus pneumoniae. Nonencapsulated mutants of these organisms are avirulent, i.e. they don't cause disease. The cell envelope is made up of two to three layers: the interior cytoplasmic membrane, the cell wall, and -- in some species of bacteria -- an outer capsule. In bacteria, the cell wall forms a rigid structure of uniform thickness around the cell and is responsible for the characteristic shape of the cell (rod, coccus, or spiral). Inside the cell wall (or rigid peptidoglycan layer) is the plasma (cytoplasmic) membrane; this is usually closely apposed to the wall layer. A layer of phospholipids and proteins, called the cytoplasmic membrane, encloses the interior of the bacterium, regulating the flow of materials in and out of the cell. This is a structural trait bacteria share with all other living cells; a barrier that allows them to selectively interact with their environment. The cytoplasm, or protoplasm, of bacterial cells is where the functions for cell growth, metabolism, and replication are carried out. It is a gel-like matrix composed of water, enzymes, nutrients, wastes, and gases and contains cell structures such as ribosomes, a chromosome, and plasmids. Plasmids, are small, extrachromosomal genetic structures carried by many strains of bacteria. Like the chromosome, plasmids are made of a circular piece of DNA. Unlike the chromosome, they are not involved in reproduction. Plasmids replicate independently of the chromosome and, while not essential for survival, appear to give bacteria a selective advantage. The nucleoid is a region of cytoplasm where the chromosomal DNA is located. It is not a membrane bound nucleus, but simply an area of the cytoplasm where the strands of DNA are found. Most bacteria have a single, circular chromosome that is responsible for replication, although a few species do have two or more. Smaller circular auxiliary DNA strands, called plasmids, are also found in the cytoplasm. Many species of bacteria have pili (singular, pilus), small hairlike projections emerging from the outside cell surface. These outgrowths assist the bacteria in attaching to other cells and surfaces, such as teeth, intestines, and rocks. Without pili, many disease-causing bacteria lose their ability to infect because they're unable to attach to host tissue. Specialized pili are used for conjugation, during which two bacteria exchange fragments of plasmid DNA. Flagella (singular, flagellum) are hairlike structures that provide a means of locomotion for those bacteria that have them. They can be found at either or both ends of a bacterium or all over its surface. The flagella beat in a propeller-like motion to help the bacterium move toward nutrients; away from toxic chemicals; or, in the case of the photosynthetic cyanobacteria; toward the light. membrane-enclosed organelle within a cell that contains the chromosomes. An array of holes, or pores, in the nuclear membrane allows for the selective passage of certain molecules (such as proteins and nucleic acids) into and out of the nucleus. https://www.genome.gov/genetics-glossary/Nucleus  A ribosome is an intercellular structure made of both RNA and protein, and it is the site of protein synthesis in the cell. The ribosome reads the messenger RNA (mRNA) sequence and translates that genetic code into a specified string of amino acids, which grow into long chains that fold to form proteins. https://shorturl.at/s22zw Alternaria (1), Fusarium (2), Mucor (3), Trichoderma (4), Penicillium (5), Paecilomyces (6).  Fungal cell wall contains 80- 90% carbohydrates, the remainder being proteins can lipids. The typical feature of fungal cells wall is presence of chitin but cellulose does occur in cell walls of Oomycetes (eg, Pythium) and hyphochytridiomycetes  Fungal membranes possess ergosterol in contrast to cholesterol found in mammalian cells. Fungal membranes, however, have the same general structure as other biological membranes, bimolecular leaflets of lipids, interspersed with proteins and glycoproteins to form a fluid mosaic.  Ribosomes translate messenger RNA into proteins. They are formed at the nucleolus and subsequently spread throughout the cytoplasm.  defined as the component of the cell internal to the cell/plasma membrane and external to the nuclear membrane. The cytoplasm of both plant and animal eukaryotic cells are composed of numerous membrane- and non- membrane bound organelles suspended in cytosol. Septa usually have little pores that are large enough to allow ribosomes, mitochondria and sometimes nuclei to flow among cells  Golgi apparatus in subapical regions of hyphae consist of paranuclear dictyosomes with 4– 5 cisternae each. Transverse and tangential sections provide ultrastructural evidence for a three-dimensional architectural model of the Golgi apparatus and a stepwise mechanism for dictyosome multiplication.  Rough and smooth ER. Commonly, the rER is involved in protein synthesis, whereas the sER has a role in lipid synthesis and Ca2+ homeostasis.  Lysosomes function as the digestive system of the cell, serving both to degrade material taken up from outside the cell and to digest obsolete components of the cell itself. The cytoskeleton plays a major role in the regulation of fungal cell morphogenesis. The fungal cytoskeleton is comprised of three polymers: F-actin, microtubules and septins.  Mitochondria are often referred to as the powerhouses of the cell because of their major role in generating cellular energy in the form of adenosine triphosphate (ATP) through the TCA cycle and the oxidative phosphorylation. The fungal vacuole is a large, membrane-bounded organelle that functions as a reservoir for the storage of small molecules (including polyphosphate, amino acids, several divalent cations (e.g. calcium), other ions, and other small molecules) as well as being the primary compartment for degradation. Contains DNA which carries the genetic code for making enzymes and other proteins used in chemical reactions such as photosynthesis and respiration.  The nucleolus is a spherical structure found in the cell's nucleus whose primary function is to produce and assemble the cell's ribosomes. The nucleolus is also where ribosomal RNA genes are transcribed. Microalgae are usually defined as a group of unicellular photosynthetic microorganisms that live in aquatic (marine and fresh water) and terrestrial environments  cell walls made up of cellulose, hemicellulose, and pectins. The inner layer is made up of cellulose, the middle layer of hemicellulose, and the outer layer of pectins. The function of the thylakoids are to assist in photosynthesis. Thylakoids synthesize ATP, adenosine triphosphate. ATP is then used in water photolysis and in the electron transport chain. They also reduce NADP+ to make NADPH, which is used with ATP in the Calvin Cycle to make long- lasting energy  Vacuole is a multifunctional compartment central to a large number of functions (storage, catabolism, maintenance of the cell homeostasis) in oxygenic phototrophs including microalgae.  In photoautotrophic microalgae, the chloroplast is a key organelle, functioning not only in photosynthesis, but also in the biosynthesis of chlorophylls, carotenoids, starch and lipids  Starch plays a central role in the life cycle as one of the principal sources of chemical energy. This polysaccharide accumulates in plastids in green algae and land plants, and both organisms have acquired various enzyme isoforms for each step of the metabolic pathway.  They help an organism in movement. They act as sensory organs to detect temperature and pH changes Nakano et al., 2023 Reynolds et al., 2017 Sogin et al. (1996). Any questions? Don't hesitate to ask for help