osmotroph

An osmotroph is an organism that obtains its nutrients by absorbing dissolved molecules through its cell membrane. This method of nutrition is in contrast to phagotrophs, which engulf solid food particles. Osmotrophy is a common mode of nutrition in many microorganisms, including bacteria, archaea, and fungi. It is also employed by some protists and even some multicellular organisms in certain life stages or environments.

The process of osmotrophy involves the transport of dissolved substances, such as amino acids, sugars, and ions, across the cell's outer boundary. This transport can occur through passive diffusion, facilitated diffusion, or active transport mechanisms. The specific molecules absorbed are typically those that are readily available in the surrounding environment, such as in soil, water, or decaying organic matter. For instance, fungi secrete enzymes into their environment to break down complex organic matter into smaller, soluble molecules that they can then absorb. Similarly, bacteria can absorb a wide range of dissolved organic and inorganic compounds depending on their metabolic capabilities. This efficient absorption strategy allows osmotrophs to thrive in diverse ecological niches where solid food sources may be scarce or inaccessible.