In cell biology

Cell biology

Cell biology is a scientific discipline that studies cells – their physiological properties, their structure, the organelles they contain, interactions with their environment, their life cycle, division and death. This is done both on a microscopic and molecular level...

, a phagosome is a vacuole

Vacuole

A vacuole is a membrane-bound organelle which is present in all plant and fungal cells and some protist, animal and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic molecules including enzymes in solution, though in certain...

 formed around a particle absorbed by phagocytosis. The vacuole is formed by the fusion of the cell membrane

Cell membrane

The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...

 around the particle. A phagosome is a cellular compartment

Cellular compartment

Cellular compartments in cell biology comprise all closed parts within a cell, usually surrounded by a single or double lipid layer membrane. Most organelles are compartments like mitochondria, chloroplasts , peroxisomes, lysosomes, the endoplasmic reticulum, the cell nucleus or the Golgi apparatus...

 in which pathogenic microorganisms can be killed and digested. Phagosomes fuse with lysosomes in their maturation process, forming phagolysosome

Phagolysosome

A phagolysosome is the membrane-enclosed organelle which forms when a phagosome fuses with a lysosome. After fusion, the food particles or pathogens contained within the phagosome are usually digested by the enzymes contained within the lysosome. Phagolysosome formation follows phagocytosis...

s.

Some bacterial pathogens that enter cells inside phagosomes either reproduce inside of the formed phagolysosome (Coxiella

Coxiella burnetii

Coxiella burnetii is an obligate intracellular bacterial pathogen, and is the causative agent of Q fever. The genus Coxiella is morphologically similar to Rickettsia, but with a variety of genetic and physiological differences. C...

spp.) or escape into the cytoplasm before the phagosome fuses with the lysosome

Lysosome

thumb|350px|Schematic of typical animal cell, showing subcellular components. [[Organelle]]s: [[nucleoli]] [[cell nucleus|nucleus]] [[ribosomes]] [[vesicle |vesicle]] rough [[endoplasmic reticulum]]...

 (Rickettsia

Rickettsia

Rickettsia is a genus of non-motile, Gram-negative, non-sporeforming, highly pleomorphic bacteria that can present as cocci , rods or thread-like . Being obligate intracellular parasites, the Rickettsia survival depends on entry, growth, and replication within the cytoplasm of eukaryotic host cells...

spp.).
Many mycobacteria, including Mycobacterium tuberculosis

Mycobacterium tuberculosis

Mycobacterium tuberculosis is a pathogenic bacterial species in the genus Mycobacterium and the causative agent of most cases of tuberculosis . First discovered in 1882 by Robert Koch, M...

and Mycobacteria avium paratuberculosis

, manipulate the host macrophage

Macrophage

Macrophages are cells produced by the differentiation of monocytes in tissues. Human macrophages are about in diameter. Monocytes and macrophages are phagocytes. Macrophages function in both non-specific defense as well as help initiate specific defense mechanisms of vertebrate animals...

to prevent nitrous acid-containing lysosomes from fusing with phagosomes and creating mature phagolysosomes. Such incomplete maturation of the phagosome maintains an environment favorable to the pathogens inside it.