3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
P89 ThE INFLuENCE OF SuRFACE
ChARACTERISTICS ON bACTERIAL CELL
ADhESION
s780
mined by the Surface Energy Evaluation system (Department
of Physical Electronics, Faculty of Science, Masaryk University,
Czech Republic).
OLGA SCHREIBEROVá, TEREZA KRULIKOVSKá,
JITKA HRDInOVá, JAn MASáK, ALEnA ČEJKOVá,
VLADIMíR JIRKů and PETR HROn
Institute of Chemical Technology Prague, Technická 5,
166 28, Praha 6, Czech Republic,
olga.schreiberova@vscht.cz
Introduction
Bacterial cell adhesion is the first step in the formation
of multicellular structure called biofilm. Biofilm is a dynamic
community of cells which display distinct properties from
the planktonic cells. These can be utilized in bioremediation
technologies1 , however the stability of adhesion must be ensured.
For this purpose, the principles of initial adhesion must
be investigated and understood.
Experimental
Microorganism.
Gram-positive pollutant degrading bacteria Rhodococcus
erythropolis CCM 2595 was obtained from the Czech
Collection of Microorganisms (Masaryk University Brno,
Czech Republic).
Cultivation and biomass determination.
Cells were cultivated in 200 ml of medium in shaked Erlenmeyer
flasks. The growth of suspended cells was monitored
as optical density at 400 nm (O.D.). Either a complex medium
nutrient broth (HiMedia, India) or minimal medium was used
(KH2PO4 0.17 g dm –3 , K2HPO4 0.13 g dm –3 , (nH4 ) 2SO4 0.71 g dm –3 , MgCl2 0.34 g dm –3 , MnCl2 1 m g dm –3 , CaCl2 0.26 m g dm –3 , FeSO4 0.6 m g dm –3 , na2MoO4 2 m g dm –3 ,
pH 7). In minimal medium phenol or glucose was used as the
only carbon and energy source.
Cell hydrophobicity.
Hydrophobicity of cells was determined by the
MATH test2 Results
T h e E x t e r n a l C o n d i t i o n s I n f l u e n c e
o n C e l l H y d r o p h o b i c i t y
Cell wall hydrophobicity reflects the cell physiological
state and is one of the most important cell characterictics that
determine the ability to adhere
•
•
•
.
• Cell fatty acids.
For fatty acids determination the cells were harvested
by centrifugation, washed and lyophilized. Fatty acids were
esterified to methyl esters, extracted to hexan and analysed
by GC-FID.
• Adhesion monitoring.
The Flow cell 81 (BioSurface Technologies, USA) was
used for assessing the adhesion of cells. Materials with different
hydrophobicity and other properties were evaluated. Three types
of glass were employed: microscope slide (labeled glass in following
text), coated glass and hydrophobized glass. Also polymeric
materials silicone and teflon were evaluated. The glass and
silicone materials were prepared at the Department of Polymers,
Faculty of Chemical Technology, Institute of Chemical Technology,
Prague.
• Material hydrophobicity.
The material hydrophobicity (except teflon) was deter-
3 . Cell hydrophobicity can be
influenced by the type of the source of carbon and energy.
In our study we investigated the effect of medium composition
(complex and minimal media, optimal and stressful
cultivation conditions). We found that the initial phenol concentration
0.3 g dm –3 can be considered as optimal and that
phenol concentration 0.7 g dm –3 partially inhibits the growth
and can be called stressful (data not shown). Concentration
1.0 g dm –3 caused considerable inhibition of the growth. nutrient
broth was chosen as a complex medium. Also glucose
(as a C source) in minimal medium was tested. During the
experiments, hydrophobicity of cells in different growth
phases was determined to ascertain the influence of this factor,
which according to literature, can be considerable4 .
The Rhodococcus erythropolis cells were proven to be
highly hydrophobic in all monitored media (see Fig. 1.). The
medium composition influence on variation of cell hydrophobicity
was significant. The changes in cell hydrophobicity
during the growth (exponential, stationary phase) were not
considerable and therefore the subsequent experiments were
carried out with cells in stationary phase.
100
90
80
exponential phase stationary phase
70
60
50
40
30
20
10
0
Fig. 1. The dependence of r. erythropolis cells hydrophobicity
Figure on media 1. composition
The dependence of media composition on R.
erythropolis cells hydrophobicity in two growth phases.
The fatty acid composition of cells cultivated in media
with different phenol concentration is presented in the Table I.
Results indicate that there is dependency of fatty acid composition
on initial phenol concentration.
hydrophobicity [%]
phenol 0,3g/l
phenol 0,7g/l
phenol 1,0g/l
nutrient broth
glucose 0,5
g/l