Pellicle formation in Shewanella oneidensis

School of Minerals processing and Bioengineering, Central south University, Changsha, PR China.
BMC Microbiology (Impact Factor: 2.73). 11/2010; 10(1):291. DOI: 10.1186/1471-2180-10-291
Source: PubMed


Although solid surface-associated biofilm development of S. oneidensis has been extensively studied in recent years, pellicles formed at the air-liquid interface are largely overlooked. The goal of this work was to understand basic requirements and mechanism of pellicle formation in S. oneidensis.
We demonstrated that pellicle formation can be completed when oxygen and certain cations were present. Ca(II), Mn(II), Cu(II), and Zn(II) were essential for the process evidenced by fully rescuing pellicle formation of S. oneidensis from the EDTA treatment while Mg (II), Fe(II), and Fe(III) were much less effective. Proteins rather than DNA were crucial in pellicle formation and the major exopolysaccharides may be rich in mannose. Mutational analysis revealed that flagella were not required for pellicle formation but flagellum-less mutants delayed pellicle development substantially, likely due to reduced growth in static media. The analysis also demonstrated that AggA type I secretion system was essential in formation of pellicles but not of solid surface-associated biofilms in S. oneidensis.
This systematic characterization of pellicle formation shed lights on our understanding of biofilm formation in S. oneidensis and indicated that the pellicle may serve as a good research model for studying bacterial communities.

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    • "In Pseudomonas fluorescens, Mg2+ cation increase cell attachment and condition the structure and further development of the biofilms [46]. Cations such as Ca2+, Mn2+, Cu2+ or Zn2+ have also been found to be essential for the formation of air-liquid interface biofilms in Shewanella oneidensis[47]. In fact, when MH2 is supplemented with 20 mg/L Ca2+ and 10 mg/L Mn2+ (CAMH2 medium), a shift in biofilm production is observed (Figure 2B). "
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    • "It is worth noting that Shewanella species thrive in oxic-anoxic interfaces, where redox conditions change rapidly with frequent shifts in the main electron acceptors11. It has been demonstrated that oxygen can affect the formation and three-dimensional structure of a community formed by Shewanella species, such as pellicles at air-liquid interfaces, aggregates in aerobic chemostat cultures and biofilms in hydrodynamic flow cells121314. Biofilms formed under aerobic conditions show a hollow and seeding dispersal structure, while a round and densely-packed structure under anaerobic conditions15. "
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