Bacterial Cellulose as a Substrate for Microbial Cell Culture

Abstract

Bacterial cellulose (BC) has a range of structural and physicochemical properties that make it a particularly useful material for the culture of bacteria. We studied the growth of 14 genera of bacteria on BC substrates produced by Acetobacter xylinum and compared the results to growth on the commercially available biopolymers agar, gellan, and xanthan. We demonstrate that BC produces rates of bacterial cell growth that typically exceed those on the commercial biopolymers and yields cultures with higher titers of cells at stationary phase. The morphology of the cells did not change during growth on BC. The rates of nutrient diffusion in BC being higher than those in other biopolymers is likely a primary factor that leads to higher growth rates. Collectively, our results suggest that the use of BC may open new avenues in microbiology by facilitating bacterial cell culture and isolation.T he introduction of agar as a substrate for bacterial culture in 1882 was an innovation that continues to have a major impact on the microbiology field over a century later (1). A major component of the cell wall of red algae (e.g., the genera Gelidium and Gracilaria), agar consists of monomers of 3,6-anhydro-L-galactose, D-galactose, and L-galactose that are connected by ␤-(1,4) and ␣-(1,3) bonds. The preparation of agar for microbial cell culture involves decreasing the temperature of a solution of agar below its melting temperature (T m ) (typically ϳ50°C), which produces a disordered gel network in which a large volume fraction of water is bound to the hydrophilic polymer chains of agar. Agar has a range of physicochemical characteristics that have made it a widely used material for the culture of microbes, namely, (i) thermal stability, (ii) optical transparency, (iii) biocompatibility, (iv) resistance to degradation by many microorganisms, and (v) availability (2).Agar is by no means an ideal material for all microbiological studies, and its application has been limited by several salient characteristics. First, a number of bacterial species grow poorly or slowly on agar, including Edwardsiella tarda, Klebsiella oxytoca, Klebsiella pneumoniae, Shigella boydii, Shigella flexneri, Staphylococcus saprophyticus, Yersinia enterocolitica, Haemophilus parainfluenzae, Sinorhizobium meliloti, and Bradyrhizobium japonicum (3, 4). Second, agar is a heterogeneous polymer due to variability in the chain length and composition of the polysaccharide. This characteristic can be problematic, as the physicochemical properties of agar vary between manufacturers and batches, which complicates experimental outcomes and reproducibility in phenotypic studies (5, 6). Third, agar is not inert to all bacteria-several genera of bacteria, including Streptomyces, Vibrio, Pseudoalteromonas, Thalassomonas, Alteromonas, Agarivorans, and Microbulbifer, produce and secrete extracellular galactosidases that degrade the hydrogel, which limits its application in bacterial isolation and culture (7). Finally, the costs of harvesting algae and the subsequent proces...

Type IV pili mechanochemically regulate virulence factors in Pseudomonas aeruginosa

“…We found that the PaQa reporter was induced upon growth on all hydrogels tested compared with induction in liquid, including agarose, gellan, alginate, and polyvinylalcohol-polyvinylpyrrolidone (PVA-PVP) hydrogels (Fig. 1B) (14,15). We conclude that PaQa expression is stimulated by physical properties of surfaces rather than their chemistry, because these hydrogels harbor distinct chemical moieties.…”

Clinical bacteriology in low-resource settings: today's solutions

“…[94][95][96] Alternatives for sheep blood, horse blood, and rabbit plasma should be explored; for example, goat, pig, and hair sheep (a breed of sheep adapted to tropical climates) blood are alternatives to sheep blood for homemade culture media, 97,98 but lyophilised or synthetic media should also be considered. Likewise, agar (ie, solidifying substrate in culture media) is obtained from sea algae at a few harvesting sites; substrates such as cellulose produced by engineered bacteria 99 should be assessed as a commercial alternative.…”

Complete genome analysis of Gluconacetobacter xylinus CGMCC 2955 for elucidating bacterial cellulose biosynthesis and metabolic regulation

“… 10 ), K. nataicola RZS01 11 , and Gluconobacter oxydans DSM 3504 were sequenced completely. Gluconacetobacter xylinus (formerly Acetobacter xylinum ) is one of the most commonly studied species because of its ability to produce relatively large amounts of BC from a wide range of carbon and nitrogen sources in liquid culture 3 , 4 , 12 and has become the most popular strain so far for manufacturing of various materials, including paper 13 , food packaging 14 , medical materials 15 , and cell culture 16 . It is difficult to obtain high productivity by means of G. xylinus in a large-scale fermentation system owing to its low yield under agitated culture.…”