Microorganisms attach to surfaces and develop biofilms. Biofilm-associated cells can be differentiated from their suspended counterparts by generation of an extracellular polymeric substance (EPS) matrix, reduced growth rates, and the up- and down- regulation of specific genes. Attachment is a complex process regulated by diverse characteristics of the growth medium, substratum, and cell surface. An established biofilm structure comprises microbial cells and EPS, has a defined architecture, and provides an optimal environment for the exchange of genetic material between cells. Cells may also communicate via quorum sensing, which may in turn affect biofilm processes such as detachment. Biofilms have great importance for public health because of their role in certain infectious diseases and importance in a variety of device-related infections. A greater understanding of biofilm processes should lead to novel, effective control strategies for biofilm control and a resulting improvement in patient management.

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Biofilms: microbial life on surfaces.

Many microorganisms, especially bacteria, produce biosurfactants when grown on water-immiscible substrates. Biosurfactants are more effective, selective, environmentally friendly, and stable than many synthetic surfactants. Most common biosurfactants are glycolipids in which carbohydrates are attached to a long-chain aliphatic acid, while others, like lipopeptides, lipoproteins, and heteropolysaccharides, are more complex. Rapid and reliable methods for screening and selection of biosurfactant-producing microorganisms and evaluation of their activity have been developed. Genes involved in rhamnolipid synthesis (rhlAB) and regulation (rhlI and rhlR) in Pseudomonas aeruginosa are characterized, and expression of rhlAB in heterologous hosts is discussed. Genes for surfactin production (sfp, srfA, and comA) in Bacillus spp. are also characterized. Fermentative production of biosurfactants depends primarily on the microbial strain, source of carbon and nitrogen, pH, temperature, and concentration of oxygen and metal ions. Addition of water-immiscible substrates to media and nitrogen and iron limitations in the media result in an overproduction of some biosurfactants. Other important advances are the use of water-soluble substrates and agroindustrial wastes for production, development of continuous recovery processes, and production through biotransformation. Commercialization of biosurfactants in the cosmetic, food, health care, pulp- and paper-processing, coal, ceramic, and metal industries has been proposed. However, the most promising applications are cleaning of oil-contaminated tankers, oil spill management, transportation of heavy crude oil, enhanced oil recovery, recovery of crude oil from sludge, and bioremediation of sites contaminated with hydrocarbons, heavy metals, and other pollutants. Perspectives for future research and applications are also discussed.

Microbial production of surfactants and their commercial potential.

INTRODUCTION 149 TAXONOMY 149 Historical Features 149 Current Taxonomic Status 149 Delineation of Species 149 Species of Clinical Importance 150 LABORATORY IDENTIFICATION 150 Isolation from Clinical Specimens 150 Morphological, Cultural, and Metabolic Characteristics 151 Species Identification 151 NOSOCOMIAL INFECTIONS CAUSED BY ACINETOBACTER SPP. 152 Overview 152 Respiratory Infection 152 Bacteremia 153 Meningitis 153 Urinary Tract Infection 154 Other Miscellaneous Infections 154 PATHOGENESIS OF ACINETOBACTER INFECTIONS 154 Predisposing Factors 154 Virulence of Acinetobacter spp. 154 EPIDEMIOLOGY 155 Human Carriage 155 Persistence in the Hospital Environment 155 TYPING SYSTEMS 156 Biotyping 156 Antibiograms 156 Serotyping 156 Phage Typing 157 Bacteriocin Typing 157 Protein Profiles 157 Multilocus Enzyme Electrophoretic Typing 157 Plasmid Profiles 157 Analysis by Pulsed-Field Gel Electrophoresis 157 Ribotyping 157 PCR-Based Methods 158 CLINICAL ANTIBIOTIC RESISTANCE 158 BIOCHEMICAL AND GENETIC MECHANISMS OF ANTIBIOTIC RESISTANCE 158 Genetics of Resistance 158 b-Lactams 159 Aminoglycosides 159 Quinolones 160 Other Antibiotics 160 THERAPY OF ACINETOBACTER INFECTIONS 160 CONCLUSIONS 160 ACKNOWLEDGMENTS 161 REFERENCES 161

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Acinetobacter spp. as nosocomial pathogens: microbiological, clinical, and epidemiological features.

Surfactants are surface-active compounds capable of reducing surface and interfacial tension at the interfaces between liquids, solids and gases, thereby allowing them to mix or disperse readily as emulsions in water or other liquids. The enormous market demand for surfactants is currently met by numerous synthetic, mainly petroleum-based, chemical surfactants. These compounds are usually toxic to the environment and non-biodegradable. They may bio-accumulate and their production, processes and by-products can be environmentally hazardous. Tightening environmental regulations and increasing awareness for the need to protect the ecosystem have effectively resulted in an increasing interest in biosurfactants as possible alternatives to chemical surfactants. Biosurfactants are amphiphilic compounds of microbial origin with considerable potential in commercial applications within various industries. They have advantages over their chemical counterparts in biodegradability and effectiveness at extreme temperature or pH and in having lower toxicity. Biosurfactants are beginning to acquire a status as potential performance-effective molecules in various fields. At present biosurfactants are mainly used in studies on enhanced oil recovery and hydrocarbon bioremediation. The solubilization and emulsification of toxic chemicals by biosurfactants have also been reported. Biosurfactants also have potential applications in agriculture, cosmetics, pharmaceuticals, detergents, personal care products, food processing, textile manufacturing, laundry supplies, metal treatment and processing, pulp and paper processing and paint industries. Their uses and potential commercial applications in these fields are reviewed.

Potential commercial applications of microbial surfactants.

Research and development of antimicrobial materials for food applications such as packaging and other food contact surfaces is expected to grow in the next decade with the advent of new polymer materials and antimicrobials. This article reviews the different types of antimicrobial polymers developed for food contact, commercial applications, testing methods, regulations and future trends. Special emphasis will be on the advantages/disadvantages of each technology.

Review of antimicrobial food packaging

Adherence of bacteria to hydrocarbons: A simple method for measuring cell‐surface hydrophobicity

Bacterial adherence to hydrocarbons (BATH) is a simple and rapid technique for determining cell-surface hydrophobicity. During recent years, this method has found application in the study of the surface characteristics of a wide variety of bacteria and bacterial mixtures. Correlations have been found between the adherence of bacteria to hydrocarbons and their attachment to other surfaces, including non-wettable plastics, epithelial cells, and teeth. A slight modification of the assay enables the isolation of nonhydrophobic mutants. The present publication briefly describes the technique and its modifications, summarizes results obtained using this method, and suggests several directions for further investigation.

Bacterial adherence to hydrocarbons: a useful technique for studying cell surface hydrophobicity

Forty-one subjects with bad breath were assessed for oral malodor and periodontal status on three occasions, at intervals of approximately one week. Oral malodor was assessed by measurement of peak and steady-state volatile sulphide levels with a portable sulphide monitor and by organoleptic measurement of whole-mouth, tongue dorsum, and interproximal dental odors by two independent judges. Reproducibility of measurements, assessed by paired t tests and Kappa testing, demonstrated no significant differences between any ofthe test results from the first and second appointments. Steady-state sulphide levels were the most reproducible of all tests. The ability of the tests to detect an expected reduction of malodor following a 0.2% chlorhexidine mouthrinse regimen was investigated by comparison of test values between the second and third appointments. Following the mouthrinsing treatment, 43% reductions of peak, 47% reductions of steady-state volatile sulphide levels, and 15-58% reductions in all other measu...

Reproducibility and Sensitivity of Oral Malodor Measurements with a Portable Sulphide Monitor

The last decade has seen a dramatic rise in scientific interest in the field of bacterial adhesion and related subjects. Much of this interest has been directed in search of “specific interactions” between bacterium and substratum, such as those that are inhibited by specific sugar moieties. A second avenue of research has been the study of the role of less specific, hydrophobic interactions. Since it appears that this second avenue of research is being increasingly followed, reviews dealing with bacterial hydrophobicity and adhesion should be of use. The aims of the present chapter are to (1) present some relevant aspects of hydrophobic interactions; (2) describe the methodology available for measurements related to bacterial cell-surface hydrophobicity and the parameters they may measure; (3) discuss investigations dealing with surface components that promote or reduce bacterial hydrophobicity; and (4) survey studies related to the role of hydrophobic interactions in mediating bacterial adhesion to interfaces, traversing areas of environmental and medical interest.

Hydrophobic interactions: role in bacterial adhesion

Microbial cell surface hydrophobicity: history, measurement and significance Nature of the hydrophobic effect Microbial hydrophobicity and fermentation technology Role of hydrophobic interactions in microbial adhesion to plastics used in medical devices Hydrophobicity of proteins and bacterial fimbriae Adhesion of bacteria to plant cells Hydrophobicity in the aquatic environment Changes in bacterial surface hydrophobicity during morphogenesis and differentiation Cell surface hydrophobicity of medically important fungi, especially Candida species Significance of hydrophobicity in the adhesiveness of pathogenic Gram-negative bacteria Hydrophobic characteristics of Staphylococci Relative importance of surface free energy as a hydrophobicity measure in bacterial adhesion to solid surfaces Hydrophobicity of Group A Streptococci to host cells Hydrophobicity of oral bacteria

Mel Rosenberg

Papers

Adherence of bacteria to hydrocarbons: A simple method for measuring cell‐surface hydrophobicity

Bacterial adherence to hydrocarbons: a useful technique for studying cell surface hydrophobicity

Reproducibility and Sensitivity of Oral Malodor Measurements with a Portable Sulphide Monitor

Hydrophobic interactions: role in bacterial adhesion

Microbial cell surface hydrophobicity