Two Morphological Types of Cell Appendages on a Strongly Adhesive Bacterium, Acinetobactersp. Strain Tol 5

Abstract

Two morphological types of appendages, an anchor-like appendage and a peritrichate fibril-type appendage, have been observed on cells of an adhesive bacterium, Acinetobacter sp. strain Tol 5, by use of recently developed electron microscopic techniques. The anchor extends straight to the substratum without branching and tethers the cell body at its end at distances of several hundred nanometers, whereas the peritrichate fibril attaches to the substratum in multiple places, fixing the cell at much shorter distances.Microbial adhesion is detrimental to both human life and industrial processes, causing infection and contamination by pathogens, dental decay, and biofilm formation, but it can also be beneficial in some environmental bioprocesses and in agriculture (5). Therefore, microbial adhesion has attracted much attention from researchers in various fields (2,5,8,20). Exopolymeric substances (EPS) (10,11,14,17) and proteinaceous appendages such as pili (4, 21) and flagella (3, 9) have been shown to be responsible for tenacious bacterial adhesion by forming a bridge between a cell and a surface. We previously isolated a rod-shaped, gram-negative, toluene-degrading bacterium, strain Tol 5, which was classified as Acinetobacter sp. (genomospecies 10) by 16S rRNA sequence analysis and physiological tests using the Micro Station system (BIOLOG) (13). This strain has a highly hydrophobic cell surface and is highly adhesive to solid surfaces. We have found that this adhesive property is beneficial to a biofiltration process for treating off gas containing volatile organic chemicals such as toluene because it allows the effective immobilization and accumulation of these bacterial cells with their high degradation activity on carrier materials. In the current study, we describe the cell appendages that mediate the adhesion of this bacterium to a solid surface.Bacterial cell appendages and EPS have been visualized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Compared with SEM, TEM provides high-resolution images by operating at higher electron-accelerating voltages (usually 70 to 100 kV for biotic samples). Of the several TEM techniques that have been used to observe living specimens (7,11,16,17), negative staining methods produce images that reflect the intact morphology of cell surface structures; such structures are unaffected by sample preparation because, in this method, the sample is mounted on a grid and subjected to electron staining without any other pretreatment. Indeed, many researchers have used TEM coupled with negative staining to visualize bacterial cell surface appendages involved in cell adhesion (9,12,15,21).To observe the cell surface structure of Tol 5 by TEM, the cells were grown until stationary phase at 28°C in 20 ml of a basal salt medium (Na 2 HPO 4 , 4.9 g; KH 2 PO 4 , 2.0 g; (NH 4 .2]) supplemented with 10 l of toluene in a 100-ml Erlenmeyer flask (13). To the flask were added four pieces (1.15 by 1.15 by 1.00 cm) of sponge carrier made of polyurethane, wit...

Effectiveness of exopolysaccharides and biofilm forming plant growth promoting rhizobacteria on salinity tolerance of faba bean (Vicia faba L.)

“…Moreover, increasing the production of exopolysaccharide against higher salt stress leads to support biofilm formation (Ishii et al, 2004;Fujishige et al, 2006). These results are in agreement with those obtained by Arora et al (2010), Qurashi and Sabri (2012), Deng et al (2015) and Kasim et al (2016).…”

Effect of Cell Appendages on the Adhesion Properties of a Highly Adhesive Bacterium,Acinetobactersp. Tol 5

“…All procedures for pretreatment of cells and for field emission scanning electron microscopy (FE-SEM) were carried out as described in a previous paper. 4) Transmission electron microscopy (TEM) of cells that were negatively stained with phosphotungstic acid was also performed, as described previously. 4) Swarming and swimming tests.…”

“…4) Transmission electron microscopy (TEM) of cells that were negatively stained with phosphotungstic acid was also performed, as described previously. 4) Swarming and swimming tests. Swarming agar plates were prepared using M8 salt supplemented with 0.2% (w/v) glucose and 0.05% (w/v) glutamate, and solidified with 0.6% (w/v) agar.…”

“…We found two morphological types of appendages that have the function of connecting the Tol 5 cells to a substratum, an anchor-like appendage and a peritrichate fibril-type appendage. 4) Contemporary electron microscopy techniques revealed that the former extends straight to the substratum without branching and tethers the cell body at its end from distances of several hundred nanometers, whereas the latter attaches to the substratum in multiple places, fixing the cell at shorter distances. Cell appendages have been shown to be involved in bacterial adhesion, 5) but the nature of the long-distance interactions between bacterial cells and a substratum mediated by appendages, such as the anchor in Acinetobacter sp.…”

Safety Assessment of Transgenic Organisms, Volume 4

“…In Acinetobacter sp. strain Tol 5, two morphological types of appendages, an anchor-like appendage and a peritrichate fibril-type appendage, have been observed on cells of an adhesive bacterium by use of electron microscopic techniques, and both are involved in adherence by this Tol 4 (Ishii et al, 2004). In A. baumannii, the presence of pili-like structures on the surface of A. baumannii ATCC 19606 cells was also shown to be essential in the early steps of the process that leads to the formation of biofilm structures on plastic surfaces (Tomaras et al, 2003), and E3, an 854 kDa surface-expressed protein homologous to the staphylococcal biofilm-associated protein, is directly involved in biofilm formation by an A. baumanni isolated from bloodstream and may be involved in intercellular adhesion within the mature biofilm (Loehfelm et al, 2008).…”