Adhesive properties of a symbiotic bacterium from a wood-boring marine shipworm

Induction of Chitin-Binding Proteins during the Specific Attachment of the Marine Bacterium Vibrio harveyi to Chitin

Previous work has shown that attachment of Vibrio harveyi to chitin is specific and involves at least two chitin-binding peptides. However, the roles and regulation of these chitin-binding peptides in attachment are still unclear. Here we show that preincubation with the oligomeric sugars composing chitin stimulated chitinase activity, cellular attachment to chitin, and production of chitin-binding peptides. One of these peptides, a 53-kDa peptide, is produced constitutively and appears to mediate initial attachment to chitin. Synthesis of another peptide, a 150-kDa chitin-binding peptide, is induced by chitin and thus may be involved in time-dependent attachment. Coordinated regulation of attachment and degradation of chitin may give bacteria like V. harveyi a selective advantage over other bacteria in nutrient-poor aquatic environments.

Adhesion of Lactobacillus amylovorus to Insoluble and Derivatized Cornstarch Granules

Approximately 70% of the cells in a suspension of the amylolytic bacterium Lactobacillus amylovorus bind to cornstarch granules within 30 min at 25 degrees C. More than 60% of the bound bacteria were removed by formaldehyde (2%) or glycine (1 M) at pH 2.0. More than 90% of the bound bacteria were removed by MgCl(2) (2 M; pH 7.0). Binding of L. amylovorus to cornstarch was inhibited in heat-killed cells and in cells that had been pretreated with glutaraldehyde, formaldehyde, sodium azide, trypsin, or 1% soluble potato starch. Bacterial binding to cornstarch appeared to correlate with both the concentration of cornstarch in the suspension and the amylose content in the granules. The ability of L. amylovorus to adhere to cornstarch granules was reduced for granules that had been extracted with HCl-ethanol, HCl-methanol, HCl-propanol, or HCl-butanol. Chemical derivatization of cornstarch resulted in a wide variety of adhesion responses by these bacteria. For example, 2-O-butyl starch (degree of substitution, 0.09) enhanced adhesion, whereas two palmitate starches (degree of substitution, 0.48 and 0.09) exhibited reduced adhesion activities. 2-O-(2-hydroxybutyl) starch and starch-poly(ethylene-co-acrylic acid) ester showed adhesion activities similar to those of the nonderivatized starch controls.

Role of Chitin-Binding Proteins in the Specific Attachment of the Marine Bacterium Vibrio harveyi to Chitin

We examined the mechanism of attachment of the marine bacterium Vibrio harveyi to chitin. Wheat germ agglutinin and chitinase bind to chitin and competitively inhibited the attachment of V. harveyi to chitin, but not to cellulose. Bovine serum albumin and cellulase do not bind to chitin and had no effect on bacterial attachment to chitin. These data suggest that this bacterium recognizes specific attachment sites on the chitin particle. The level of attachment of a chitinase-overproducing mutant of V. harveyi to chitin was about twice as much as that of the uninduced wild type. Detergent-extracted cell membranes inhibited attachment and contained a 53-kDa peptide that was overproduced by the chitinase-overproducing mutant. Three peptides (40, 53, and 150 kDa) were recovered from chitin which had been exposed to membrane extracts. Polyclonal antibodies raised against extracellular chitinase cross-reacted with the 53- and 150-kDa chitin-binding peptides and inhibited attachment, probably by sterically hindering interactions between the chitin-binding peptides and chitin. The 53- and 150-kDa chitin-binding peptides did not have chitinase activity. These results suggest that chitin-binding peptides, especially the 53-kDa chitin-binding peptide and chitinase and perhaps the 150-kDa peptide, mediate the specific attachment of V. harveyi to chitin.

Adhesion and growth rate of Clostridium cellulolyticum ATCC 35319 on crystalline cellulose

The rate of tritiated-thymidine incorporation into DNA was used to estimate Clostridium cellulolyticum H10 growth rates on Avicel cellulose, taking into consideration both the unattached cells and the cells adhered to the substrate. The generation time on cellobiose calculated from the data on cell density (4.5 h) agreed well with the generation time calculated by tritiated-thymidine incorporation (3.8 h). Growth on Avicel cellulose occurred when bacteria were adhered to their substrate; 80% of the biomass was detected on the cellulose. Taking into consideration attached and free bacteria, the generation time as determined by thymidine incorporation was about 8 h, whereas by bacterial-protein estimation it was about 13 h. In addition to the growth rate of the bacteria on the cellulose, the release of adhered cells constituted an important factor in the efficiency of the cellulolysis. The stage of growth influenced adhesion of C. cellulolyticum; maximum adhesion was found during the exponential phase. Under the conditions used, the end of growth was characterized by an acute release of biomass and cellulase activity from the cellulose. An exhaustion of the accessible cellulose could be responsible for this release.

Binding of Extracellular Carboxymethylcellulase Activity from the Marine Shipworm Bacterium to Insoluble Cellulosic Substrates

The binding of extracellular endoglucanase, a carboxymethylcellulase (CMCase), produced by the marine shipworm bacterium to insoluble cellulose substrates was investigated. Up to 70% of CMCase activity bound to cellulosic substrates, and less than 10% bound to noncellulosic substrates. CMCase binding to cellulose was enhanced in basal salt medium or sodium phosphate buffer containing 0.5 M NaCl. Increased cellulose particle size correlated with decreased CMCase binding. Also, cellulose treated with either 5 N NaOH or commercial cellulase reduced the CMCase binding to these surfaces. Pretreatment of CMCase preparations with 0.01% sodium dodecyl sulfate, 5% β-mercaptoethanol, and 5 mM EDTA or ethylene glycol-bis(β-aminoethyl ether)- N,N,N′,N′ -tetraacetic acid (EGTA) had little effect on binding to cellulose. While pretreatment of CMCase with trypsin, chymotrypsin, and pronase had little effect on CMCase enzymatic activity, the ability to bind to cellulose was greatly diminished by these treatments.

The presence, nature, and role of gut microflora in aquatic invertebrates: A synthesis

This review of the literature concerns the gut microbiota of aquatic invertebrates and highlights the questions and processes that merit attention if an understanding of the role of gut microbes in the physiology of host invertebrates and nutrient dynamics of aquatic systems is to be gained. A substantial number of studies report the presence of gut microbes in aquatic invertebrates. Crustacea, Mollusca, and Echinodermata have received the most attention, with few studies involving other invertebrate groups. Different types of associations (e.g., ingestion, contribution of exoenzymes, incubation, parasitism) are reported to occur between gut microbes and aquatic invertebrates, and it is clear that gut bacterial communities cannot be treated as single functional entities, but that individual populations require examination. In addition, gut microbes may be either ingested transients or residents, the presence of which have different implications for the invertebrate. The most commonly reported genera of gut bacteria are Vibrio, Pseudomonas, Flavobacterium, Micrococcus, and Aeromonas. Quite a number of authors report the physiological properties of gut microbes (including enzyme activities and attributes such as nitrogen fixation), while less attention has been given to consideration of the colonization sites within the digestive tract, the density and turnover of gut bacteria, and the factors affecting the presence and nature of gut microflora. In addition, although a few studies have demonstrated a positive relationship between invertebrates and their gut microbiota, particularly with regard to nutrient gain by the invertebrate, very little conclusive evidence exists as to the role of bacteria in the physiology of host invertebrates. This has resulted from a lack of process-oriented studies. The findings for aquatic gut microbes are compared to those of gut bacteria associated with terrestrial invertebrates, where gut microbes contribute significantly to nutrient gain by the host in some environments.