Keith E. Cooksey

Biofilms and microbial fouling

Publisher Summary This chapter presents a framework for understanding the process of biofilm development on a surface and the consequences of the accumulation on the environment. It begins by describing biofilm development in terms of selected fundamental rate processes and environmental parameters influencing their rate and extent. The physical, chemical, and biochemical properties of the biofilm that determine the influence of the biofilm on its microenvironment are discussed in the chapter. The properties of the biofilm and its microenvironment lead to a discussion of the microbial ecology within the biofilm and the physiology of the organisms immobilized within it. The effects of the biofilm on its environment, both beneficial and detrimental, are presented. There are many other questions and concerns stated in this chapter regarding biofilm processes.

Use of Fluorophore-Conjugated Lectins To Study Cell-Cell Interactions in Model Marine Biofilms

ABSTRACT Biofilms dominated by pennate diatoms are important in fields as diverse as ship biofouling and marine littoral sediment stabilization. The architecture of a biofilm depends on the fact that much of its mass consists of extracellular polymers. Although most illuminated biofilms in nature are dominated by phototrophs, they also contain heterotrophic bacteria. Given the close spatial association of the two types of organisms, cell-cell interaction is likely. Fluorophore-conjugated lectins were used to demonstrate the sites of the various extracellular polymers in three species of diatoms. Based on their lectin staining properties, the polymers in different species appeared to be similar, but their involvement in the process of attachment to a surface differed. In a coculture Pseudoalteromonas sp. strain 4 or its sterilized spent medium reduced the ability of Amphora coffeaeformis and Navicula sp. strains 1 and D to adhere, inhibited motility, and caused agglutination and eventually diatom cell lysis. Diatoms could be protected from the negative effects of the bacterial spent medium if d-galactose or mannan was included in the incubation medium. The active principle of the spent medium is probably a lectin/agglutinin that is able to bind to the extracellular polymers of the diatoms that are involved in adhesion and motility. Awareness of interactions of this type is important in the study of natural biofilms.

ISOLATION AND PHYSIOLOGICAL STUDIES ON THREE ISOLATES OF AMPHORA (BACILLARIOPHYCEAE)1

Three clones of the diatom Amphora were euryhaline, able to grow autotrophically at 160 lx (0.001 ly/min) and heterotrophically on glucose and fructose. Furthermore 2 clones grew on glutamate and feast extract. Light‐limited growth of individual clones was stimulated by glycerol, galactose, lactate, acetate, aspartate and asparagine, although mannose torn inhibitory at low and high light levels. The half‐saturation constant for growth of A. coffeaefomis var. perpusilla Grunow (Cleve) with glucose was 25 μM. Heterotrophic growth rate of this organism became saturated with respect to glucose at 0.5 mM.

GROWTH‐INFLUENCING SUBSTANCES IN SEDIMENT EXTRACTS FROM A SUBTROPICAL WETLAND: INVESTIGATION USING A DIATOM BIOASSAY

A Biological assay using Amphora coffeaeformis var. perpusilla (Grunow) Cleve and A. coffeaeformis (Agardh) Kützing was used to investigate the changes in the properties of soluble organic carbon in sediments taken from a coastal wetland. During January to May, sediment extracts became increasingly inhibitory to diatom growth After the onset of the spring rains, the inhibitory properties of the extracts disappeared. Substances capable of promoting mixotrophic growth and heterotrophic growth were found in extracts taken in July to December. These positive responses took place at the time of mangrove (Rhizophora mangle L.)leaf‐fall.

ACETATE METABOLISM BY WHOLE CELLS OF PHAEODACTYLUM TRICORNUTUM BOHLIN12

Both morphological forms of Phaeodactylum tricornutum incorporated acetate in the light and in darkness. In the dark, the majority of the acetate was oxidized, probably by the tricarboxylic acid cycle. Although some CO2 was formed from acetate in the light, most acetate carbon was found in the cellular lipids. Acetate incorporation in the light was probably a result of both direct and indirect assimilation. The organism grew poorly on acetate in the light at a very low CO2 tension.

CALCIUM DEFICIENCY CAN INDUCE THE TRANSITION FROM OVAL TO FUSIFORM CELLS IN CULTURES OF PHAEODACTYLUM TRICORNUTUM BOHLIN1,2

The diatom Phaeodactylum tricornutum Bohlin is known to be pleomorphic. Previously it was considered that growth on medium solidified with agar produced ovate cells, whereas growth in liquid medium gave rise to fusiform cells. We have shown that ovate cells can be propagated in liquid medium if the calcium content of the medium is below 15 mg/liter. If the concentration of calcium is raised, fusiform cells develop.

THE GLUCOSE TRANSPORT SYSTEM OF AMPHORA COFFEAEFORMIS (BACILLARIOPHYCEAE)1

Amphora coffeaeformis (Ag.) Kütz. var. perpusilla (Grun.) Cleve took up glucose by an inducible transport system. The system was induced by d‐fructose, d‐mannose, as well as glucose. Some d‐pentoses also induced a glucose uptake system but it may not be the same one as that induced by hexose. d‐fructose, d‐mannose and 2‐deoxy‐d‐glucose inhibited 2 mM glucose uptake at equimolar concentration, but d‐pentoses did not. The uptake system decayed in ca. 5 h in the absence of glucose. The half‐saturation constant for uptake, K8 was ca. 0.1 mM glucose with a maximum uptake rate, Vmax= 0.4 nmol/106 cells‐min−1.