B. pseudomallei and B. thailandensis form
biofilms under different temperatures
We assessed the ability of Burkholderia to form a biofilm under a
scanning electron microscope (SEM) using B. pseudomallei JW270
strain. We depict that the biofilm formation process inBurkholderia follows the same pattern as most Gram-negative
bacteria (Fig 1a). We see single cells adhere to each other (Fig 1a,
step 1). The adherence is followed by colony aggregation (Fig 1a, step
2) and export of the biofilm components (Fig 1a, steps 3-4). Export of
biofilm components progresses until most cells are covered/protected to
form a mature biofilm (Fig 1a, step 5). Cells are dispersed from a
matured biofilm to continue the cycle (Fig 1a, step 6). A visual and
microscopic observation shows that all four strains used for the
composition study: B. pseudomallei strains (Bp1026b Δasd ,
Bp82, and JW270) and B. thailandensis E264 are all able to form
both an adherent biofilm at the bottom of the plate and a pellicle; a
biofilm formed at the air-liquid interface (Fig 1b). We observed that
pellicle morphologies differed between strains. Bp82 and JW270 present
wrinkled and cloudy pellicles while
1026b Δasd and E264 have a
thin, smooth layer (Fig. 1b). Fig 1c shows an image of a processed JW270
pellicle. There was no difference in the SEM images between all
pellicles.
B. pseudomallei is not fastidious and can grow under diverse
environmental conditions [41], such as soil and rice paddy field
water at temperatures between 21°C and 37°C [42, 43]. B.
pseudomallei in the lab is commonly grown at 37°C, a temperature that
corresponds to human body temperature [44]. To compare biofilm
capabilities under varying temperatures, B. pseudomallei was
grown statically for 72 hours either at room temperature (22°C) to
represent rice paddy fields or at 37°C in an incubator to represent
human host temperature. Fig. 1d shows that at the end of the experiment,
there is no significant difference between the same strains grown at
different temperatures (Student’s t-test, P > 0.05).
However, we observed that in earlier time points, cells grown at RT
lagged behind 37°C cells but ultimately forms the same amount of biofilm
by 72 hours. For comparison between groups at the end of the experiment
(e.g. 1026b Δasd vs. Bp82 at 37°C), student t-tests show that
there was no significant difference between biofilms formed between all
strains (Fig 1e, P >0.05). We also observed that cultures
grown at both temperatures formed surface adherent biofilms, but
cultures grown at 37°C are capable of forming both surface adherent
biofilms and pellicles.