Adherence and growth of a Bacillus species on an insoluble polyester polyurethane

• Published in: International biodeterioration & biodegradation 1998-07, Vol.42 (1), p.63-73
• Main Authors: Ii, Robert C.Blake, Norton, William N, Howard, Gary T
• Format: Article
• Language: English
• Subjects: Bacillus; Bacillus species; Biodeterioration. Biofouling; Biological and medical sciences; Biotechnology; Cell culture; Dissociation; Electric impedance measurement; Fundamental and applied biological sciences. Psychology; Growth kinetics; Industrial applications and implications. Economical aspects; Insoluble polyester polyurethane; Laser Doppler velocimeters; Metabolism; Optical variables measurement; Polyurethanes; Scanning electron microscopy; Transmission electron microscopy
• ISSN: 0964-8305; 1879-0208
• DOI: 10.1016/S0964-8305(98)00048-1

Laser Doppler velocimetry, electrical impedance, and static light scattering measurements were employed to quantify the growth of a Bacillus species at the expense of a heterogeneous, insoluble polyester polyurethane. Progress of the culture was arbitrarily divided into 3 phases: adherence of polyurethane to the bacteria, bacterial multiplication, and aggregation of the bacteria with the remaining, undegraded polymer. Observations with all 3 instruments indicated that multiple binding of the small colloidal polyurethane to the bacterium occurred over the course of 4 to 5 hours. During this extended lag period, the average volume of the bacterium–polyurethane complex increased to nearly three times that of the bacterium alone. The Bacillus cells then entered an exponential phase of growth with a doubling time of 55 minutes. Beyond 8 hours, the number of free bacteria in the culture declined concomitant with the appearance of large aggregrates composed of hundreds of cells and residual polyurethane. Further culture development ceased beyond 24 hours, leaving portions of the heterogeneous substrate unmetabolized. Phase contrast, scanning electron, and transmission electron microscopic observations provided qualitative corroboration of the significant events in the culture deduced from the instrumental analyses. These data demonstrate that physical measurements of colloidal suspensions may be used to study and quantify the complex interactions of bacteria with heterogeneous insoluble substrates.