Planktonic microbial cells

Planktonic microbial cells refer to microorganisms, such as bacteria and fungi, that exist as independent, free-floating individuals in a liquid medium (Donlan, 2002). This physiological state is characterized by rapid growth and high metabolic activity, distinguishing it from the sessile state found in biofilms where microbes are encased in a protective extracellular matrix (Costerton et al., 1999). In clinical medicine, planktonic cells are the primary drivers of acute infections and are responsible for the systemic dissemination of pathogens through the bloodstream or lymphatic system, leading to conditions like bacteremia and sepsis (Hall-Stoodley et al., 2004). Most conventional antimicrobial agents, including penicillins and fluoroquinolones, are specifically developed and tested for their efficacy against planktonic populations, typically measured by the Minimum Inhibitory Concentration (MIC) (Andrews, 2001). These drugs interact with various molecular targets within the cell, such as ribosomes or cell wall synthesis enzymes, to induce cell death or inhibit growth. However, the transition of planktonic cells into biofilms often results in a significant increase in tolerance to these treatments, presenting a major challenge in treating chronic and device-associated infections (Stewart & Costerton, 2001).

Other names

Free-living microbesSuspended microbial cellsNon-adherent microbesPlanktonic bacteriaPlanktonic fungi

Antimicrobial agents target various essential cellular processes in planktonic cells, including cell wall synthesis inhibition, protein synthesis inhibition (ribosomal targeting), nucleic acid replication interference, and disruption of metabolic pathways (Andrews, 2001).