engleski

Double layer charge displacement by cell adhesion

We report the electrical attachment signals recorded in laboratory cultures of marine microflagellates and bacteria. The attachments signals are current-time transients caused by a displacement of double-layer charge at the electrode/aqueous electrolyte interface by cell adhesion during the initial attachment and spreading of a cell. Marine microflagellates with fluid cell membrane and multicellular fillaments of marine gliding bacteria Saprospira grandis were used in this study. We selected multicellular filaments (10-100 unit bacterial cells) of a few marine Saprospira isolates, since the attachment signal of a single cell could be amplified. Expanding mercury sphere electrode (dropping mercury electrode) is used as a probe. Its main advantage is: (i) an ease of varying surface charge and interfacial tension: (ii) the fluidity of the interface enhances adhesion of cells and is also typical of most marine interfaces. Initial attachment and spreading of a single Saprospira filament that reaches the electrode/electrolyte interface results in a rapid (tens of milliseconds) current transient caused by the displacement of ions and water molecules from the contact area of the interface. Amplitude and duration of each attachment signal reflect both size and interfacial reactivity of the filament. Signals were strain and growth condition specific. Oscillatory attachment signals were observed in some cases. The attachment is confined to a broad range of positive and negative charges of the electrode surface (from +19.7 to -10.6 uC/cmČ2) and it depends critically on the interfacial tension. Hydrophobic interaction could be considered as a major driving force in adhesion of Saprospira filaments at the charged mercury interface.

marine microorganisms; charge displacement; hydrophobic interaction

nije evidentirano