- Published on
Pathology – Microbes
Bacteria • Unicellular entities possessing double-stranded DNA that resides freely in the cytoplasm, encased by a cell membrane and cell wall. • Predominantly thrive in the presence of oxygen (aerobes), however are capable of growth in its absence (facultative anaerobes). Certain organisms proliferate exclusively under anoxic conditions (strict anaerobes). Gram-positive bacteria possess a robust cell wall comprised of peptidoglycan plus an additional polymer, frequently teichoic acid. Gram-negative bacteria possess a weaker peptidoglycan layer, which is covered by an outer lipid membrane consisting of lipopolysaccharide. Mycobacteria are a kind of bacteria characterized by a thick, waxy cell wall that can be stained using the Ziehl–Nielsen method.
Viruses are the smallest and most basic organisms, consisting of genetic material in the form of DNA or RNA encased within a protein shell known as a capsid. Certain viruses possess an external lipid membrane obtained from the host cell in which they originated. • Obligate intracellular entities that proliferate exclusively by infecting a host cell and commandeering its metabolic machinery. • Induce disease by damaging host cells (direct cytopathic effect) or as a result of the immunological response to the infection. • Certain viruses can induce latent infections, such as herpes simplex. • Some viruses are carcinogenic and contribute to the transformation of host cells and the onset of malignancy, for instance, HPV in cervical cancer and EBV in nasopharyngeal carcinoma.
Fungi possess DNA encased within a nucleus, feature a cell membrane that includes ergosterol, and have an external cell wall made of chitin. Yeasts are unicellular fungi that reproduce asexually through budding, such as Candida. • Moulds develop as branching filaments termed hyphae that intertwine to create a complex structure known as mycelium. Mycelia generate spores. • Certain fungi can survive in both yeast and mold forms, such as Histoplasma
Protozoa are unicellular creatures that can inhabit host cells or exist in the extracellular milieu. Intracellular protozoa obtain nourishment from the host cell (e.g., Plasmodium, Leishmania, Toxoplasma). Extracellular protozoa obtain nutrients through direct intake and/or the consumption of sloughed epithelial cells (e.g., Giardia, Trichomonas). Helminths • Complex multicellular parasitic worms that vary in size from tiny entities to colossal animals several meters long. • Numerous species possess intricate life cycles that involve multiple hosts. • Categorized as nematodes (roundworms), cestodes (tapeworms), and trematodes (flukes)
Bacteria • Unicellular entities possessing double-stranded DNA that resides freely in the cytoplasm, encased by a cell membrane and cell wall. • Predominantly thrive in the presence of oxygen (aerobes), however are capable of growth in its absence (facultative anaerobes). Certain organisms proliferate exclusively under anoxic conditions (strict anaerobes). Gram-positive bacteria possess a robust cell wall comprised of peptidoglycan plus an additional polymer, frequently teichoic acid. Gram-negative bacteria possess a weaker peptidoglycan layer, which is covered by an outer lipid membrane consisting of lipopolysaccharide. Mycobacteria are a kind of bacteria characterized by a thick, waxy cell wall that can be stained using the Ziehl–Nielsen method.
Viruses are the smallest and most basic organisms, consisting of genetic material in the form of DNA or RNA encased within a protein shell known as a capsid. Certain viruses possess an external lipid membrane obtained from the host cell in which they originated. • Obligate intracellular entities that proliferate exclusively by infecting a host cell and commandeering its metabolic machinery. • Induce disease by damaging host cells (direct cytopathic effect) or as a result of the immunological response to the infection. • Certain viruses can induce latent infections, such as herpes simplex. • Some viruses are carcinogenic and contribute to the transformation of host cells and the onset of malignancy, for instance, HPV in cervical cancer and EBV in nasopharyngeal carcinoma.
Fungi possess DNA encased within a nucleus, feature a cell membrane that includes ergosterol, and have an external cell wall made of chitin. Yeasts are unicellular fungi that reproduce asexually through budding, such as Candida. • Moulds develop as branching filaments termed hyphae that intertwine to create a complex structure known as mycelium. Mycelia generate spores. • Certain fungi can survive in both yeast and mold forms, such as Histoplasma
Protozoa are unicellular creatures that can inhabit host cells or exist in the extracellular milieu. Intracellular protozoa obtain nourishment from the host cell (e.g., Plasmodium, Leishmania, Toxoplasma). Extracellular protozoa obtain nutrients through direct intake and/or the consumption of sloughed epithelial cells (e.g., Giardia, Trichomonas). Helminths • Complex multicellular parasitic worms that vary in size from tiny entities to colossal animals several meters long. • Numerous species possess intricate life cycles that involve multiple hosts. • Categorized as nematodes (roundworms), cestodes (tapeworms), and trematodes (flukes)
0 Comments
