Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a pH stimulus with pH < 7. pH is a measure of the acidity or basicity of an aqueous solution.

Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a pH stimulus with pH < 7. pH is a measure of the acidity or basicity of an aqueous solution.

The increase in size or mass of a symbiont, occurring in its host's organelle. The host is defined as the larger of the organisms involved in a symbiotic interaction.

The process in which ammonium is transported across a membrane. Ammonium is the cation NH4+.

The rigid or semi-rigid envelope lying outside the cell membrane of plant, fungal, most prokaryotic cells and some protozoan parasites, maintaining their shape and protecting them from osmotic lysis. In plants it is made of cellulose and, often, lignin; in fungi it is composed largely of polysaccharides; in bacteria it is composed of peptidoglycan; in protozoan parasites such as Giardia species, it's made of carbohydrates and proteins.

The part of the cytoplasm that does not contain organelles but which does contain other particulate matter, such as protein complexes.

The component of the plasma membrane consisting of the gene products and protein complexes having at least some part of their peptide sequence embedded in the hydrophobic region of the membrane.

A lipid bilayer that forms the outermost membrane of the cell envelope; enriched in polysaccharide and protein; the outer leaflet of the membrane contains specific lipopolysaccharide structures.