Gram-negative bacterium in the context of "Bacterial outer membrane"

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⭐ Core Definition: Gram-negative bacterium

Gram-negative bacteria are bacteria that, unlike Gram-positive bacteria, do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is that their cell envelope consists of a thin peptidoglycan cell wall sandwiched between an inner (cytoplasmic) membrane and an outer membrane. These bacteria are found in all environments that support life on Earth.

Within this category, notable species include the model organism Escherichia coli, along with various pathogenic bacteria, such as Pseudomonas aeruginosa, Chlamydia trachomatis, and Yersinia pestis. They pose significant challenges in the medical field due to their outer membrane, which acts as a protective barrier against numerous antibiotics (including penicillin), detergents that would normally damage the inner cell membrane, and the antimicrobial enzyme lysozyme produced by animals as part of their innate immune system. Furthermore, the outer leaflet of this membrane contains a complex lipopolysaccharide (LPS) whose lipid A component can trigger a toxic reaction when the bacteria are lysed by immune cells. This reaction may lead to septic shock, resulting in low blood pressure, respiratory failure, reduced oxygen delivery, and lactic acidosis.

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Gram-negative bacterium in the context of Meningococcal infection

Neisseria meningitidis, often referred to as the meningococcus, is a Gram-negative bacterium that can cause meningitis and other forms of meningococcal disease such as meningococcemia, a life-threatening sepsis. The bacterium is referred to as a coccus because it is round, and more specifically a diplococcus because of its tendency to form pairs.

About 10% of adults are carriers of the bacteria in their nasopharynx. As an exclusively human pathogen, it causes developmental impairment and death in about 10% of cases. It causes the only form of bacterial meningitis known to occur epidemically, mainly in Africa and Asia. It occurs worldwide in both epidemic and endemic form.

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Gram-negative bacterium in the context of Bacterial flagella

A flagellum (/fləˈdʒɛləm/; pl.: flagella) (Latin for 'whip' or 'scourge') is a hair-like appendage that protrudes from certain plant and animal sperm cells, from fungal spores (zoospores), and from a wide range of microorganisms to provide motility. Many protists with flagella are known as flagellates.

A microorganism may have from one to many flagella. A gram-negative bacterium Helicobacter pylori, for example, uses its flagella to propel itself through the stomach to reach the mucous lining where it may colonise the epithelium and potentially cause gastritis, and ulcers – a risk factor for stomach cancer. In some swarming bacteria, the flagellum can also function as a sensory organelle, being sensitive to wetness outside the cell.

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LINKED FROM (PARENTS)
← Meningococcal infection ← Bacterial flagella ← Flagellum ← Flagella
LINKS TO (CHILDREN)
Pseudomonas aeruginosa → Bacteria → Gram-positive bacteria → Crystal violet → Gram stain → Cell envelope → Peptidoglycan → Gram-negative cell wall → Cytoplasm → Cell membrane → Bacterial outer membrane → Earth → Model organism → Escherichia coli → Pathogenic bacteria → Chlamydia trachomatis → Yersinia pestis → Antibiotic → Penicillin → Detergent → Antimicrobial → Lysozyme → Innate immune system → Lipid bilayer → Lipopolysaccharide → Lipid A → Lysis → Septic shock → Hypotension → Respiratory failure → Hypoxia (medical) → Lactic acidosis →