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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Available from: Haichun Gao, Oct 04, 2015
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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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    ABSTRACT: A variety of conditions (culture media, inocula, incubation temperatures) are employed in antifouling tests with marine bacteria. Shewanella algae was selected as model organism to evaluate the effect of these parameters on: bacterial growth, biofilm formation, the activity of model antifoulants, and the development and nanomechanical properties of biofilms.The main objectives were:1) To highlight and quantify the effect of these conditions on relevant parameters for antifouling studies: biofilm morphology, thickness, roughness, surface coverage, elasticity and adhesion forces.2) To establish and characterise in detail a biofilm model with a relevant marine strain. Both the medium and the temperature significantly influenced the total cell densities and biofilm biomasses in 24-hour cultures. Likewise, the IC50 of three antifouling standards (TBTO, tralopyril and zinc pyrithione) was significantly affected by the medium and the initial cell density. Four media (Marine Broth, MB; 2% NaCl Mueller-Hinton Broth, MH2; Luria Marine Broth, LMB; and Supplemented Artificial Seawater, SASW) were selected to explore their effect on the morphological and nanomechanical properties of 24-h biofilms. Two biofilm growth patterns were observed: a clear trend to vertical development, with varying thickness and surface coverage in MB, LMB and SASW, and a horizontal, relatively thin film in MH2. The Atomic Force Microscopy analysis showed the lowest Young modulii for MB (0.16 +/- 0.10 MPa), followed by SASW (0.19 +/- 0.09 MPa), LMB (0.22 +/- 0.13 MPa) and MH2 (0.34 +/- 0.16 MPa). Adhesion forces followed an inverted trend, being higher in MB (1.33 +/- 0.38 nN) and lower in MH2 (0.73 +/- 0.29 nN). All the parameters significantly affected the ability of S. algae to grow and form biofilms, as well as the activity of antifouling molecules. A detailed study has been carried out in order to establish a biofilm model for further assays. The morphology and nanomechanics of S. algae biofilms were markedly influenced by the nutritional environments in which they were developed. As strategies for biofilm formation inhibition and biofilm detachment are of particular interest in antifouling research, the present findings also highlight the need for a careful selection of the assay conditions.
    BMC Microbiology 04/2014; 14(1):102. DOI:10.1186/1471-2180-14-102 · 2.73 Impact Factor
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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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    ABSTRACT: Although oxygen has been reported to regulate biofilm formation by several Shewanella species, the exact regulatory mechanism mostly remains unclear. Here, we identify a direct oxygen-sensing diguanylate cyclase (DosD) and reveal its regulatory role in biofilm formation by Shewanella putrefaciens CN32 under aerobic conditions. In vitro and in vivo analyses revealed that the activity of DosD culminates to synthesis of cyclic diguanylate (c-di-GMP) in the presence of oxygen. DosD regulates the transcription of bpfA operon which encodes seven proteins including a large repetitive adhesin BpfA and its cognate type I secretion system (TISS). Regulation of DosD in aerobic biofilms is heavily dependent on an adhesin BpfA and the TISS. This study offers an insight into the molecular mechanism of oxygen-stimulated biofilm formation by S. putrefaciens CN32.
    Scientific Reports 06/2013; 3:1945. DOI:10.1038/srep01945 · 5.58 Impact Factor
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    ABSTRACT: Shewanella oneidensis is a highly motile organism by virtue of a polar flagellum. Unlike most flagellated bacteria, it contains only one major chromosome segment encoding the components of the flagellum with the exception of the motor proteins. In this region, three genes encode flagellinsaccording to the original genome annotation. However, we find that only flaA and flaB encode functional filament subunits. Although these two genesare under the control of different promoters, they are actively transcribed and subsequently translated, producing a considerable number of flagellin proteins. Additionally, both flagellins are able to interact with their chaperon FliS and are subjected to feedback regulation. Furthermore, FlaA and FlaB are glycosylated by a pathwayinvolving a major glycosylating enzyme,PseB, in spite of the lack of the majority of theconsensus glycosylation sites. In conclusion, flagellar assembly in S. oneidensis has novel features despite the conservation of homologous genes across taxa.
    PLoS ONE 06/2011; 6(6):e21479. DOI:10.1371/journal.pone.0021479 · 3.23 Impact Factor
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