Introductory Microbiology

Prosthecae and stalks

• Prosthaecae are semi-rigid extensions of the cell wall and cytoplasmic membrane and have a diameter that is always less than that of the cell. They are characteristic of a number of aerobic bacteria from fresh water and marine environments. Some bacterial genera such as Caulobacter have a single prosthecae; others such as Stella and Ancalamicrobium have several prostheca increase the surface area of the cells for nutrient absorption, which is advantageous in dilute environments. Some prosthecate bacteria may form a new cell at the end of a prostheca; others have an adhesive substance at the end of a prostheca that aids is attachment to surfaces.
• Although the term stalk is sometimes used interchangeably with the terms prostheca or hypha, it is perhaps better to restrict its use to certain non-living ribbon like or tubular appendages that are excreted by the cell, such as those found in the genera Gallionella or Planctomyces. These stalks aid in attachment of the cells to surfaces.