Browsing by Author "Jass, J."

Now showing 1 - 4 of 4

Assessment of a chemostat-coupled modified robbins device to study biofilms
(1995-10) Jass, J.; Costerton, J. William; Lappin-Scott, H. M.
The combination of a modified Robbins device (MRD) attached to the effluent line of a continuous cultivation vessel was assessed by the adhesion of planktonic bacteria maintained at a controlled growth rate. This combination of a chemostat and an MRD provides a large number of sample surfaces for monitoring both the formation and control of biofilms over extended periods of time. This apparatus was used to monitor the colonization of two soil isolates,Pseudomonas fluorescens (EX101) andPseudomonas putida (EX102) onto silastic rubber surfaces. At a similar μrel, both bacteria attached to the silastic, howeverP. fluorescens formed confluent, dense biofilms in less than 24 h, whereasP. putida adhered as single cells or microcolonies after the same period. The metabolic activity, measured by INT-formazan formation, was similar for both organisms with a peak at 6 h of colonization and a subsequent decrease after 24 h. Long term colonization studies ofP. fluorescens produced a population of greater than 9.5 log cfu cm−2 at 28 days demonstrating the advantages of the chemostat-MRD association. This technique proved to be successful for studying bacterial adhesion and biofilm formation in tubular devices by bacterial populations at controlled and low growth rates.
The effect of electrical currents and tobramycin on pseudomonas aeruginosa biofilms
(1995-09) Jass, J.; Costerton, J. William; Lappin-Scott, H. M.
The combined use of antibiotics with low levels of electrical current has been reported to be more effective in controlling biofilms (the bioelectric effect) than antibiotics alone. An electrical colonisation cell was designed to study the effect of antibiotics on biofilms formed on a dialysis membrane away from the electrode surface. To avoid the electrochemical generation of toxic products,Pseudomonas aeruginosa biofilms were formed in minimal salts medium that excluded chloride-containing compounds. Under these conditions, electrical currents of up to 20 mA cm−2 did not prevent biofilm formation or have any detrimental effect on an established biofilm. Tobramycin alone at concentrations of 10 μg ml−1 did not affect the biofilm, but were significantly enhanced by 9 mA cm−2. The effect of tobramycin concentrations of 25 μg ml−1 were enhanced by a 15 mA cm−2 electrical current. In both cases higher levels of electrical current, up to 20 mA cm−2, did not further enhance the effect of the antibiotic. The possible mechanisms of action of the bioelectric effect have been reported to involve electrophoresis, iontophoresis and electroporesis, thus overcoming the biofilm biomass and cell wall barriers. Our results suggest that other factors may also be important, such as the metabolic activity and growth rate of the bacteria. Such factors may be critical in maximising antibiotic efficacy.
Microbial detachment from biofilms
(2000) Moore, G. F.; Dunsmore, B. C.; Jones, S. M.; Smejkal, C. W.; Jass, J.; Stoodley, Paul; Lappin-Scott, H. M.
Screen for novel compounds/activity in the environmental protection industries
(1995) Lappin-Scott, H. M.; Jass, J.; Costerton, J. William