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.

/pdf/biofilms-microbial-life-on-surfaces-1snm9wt8v9.pdf

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

/pdf/acinetobacter-spp-as-nosocomial-pathogens-microbiological-430u90opiv.pdf

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

Whereas previous studies have shown correlations between volatile sulphur compounds (VSC) and bad breath levels, it is probable that other compounds found in the oral cavity may contribute to oral malodor. In the present investigation, the possibility that diamines (cadaverine and putrescine) are associated with oral malodor parameters was assessed. Saliva samples from 52 subjects were analyzed for cadaverine and putrescine by HPLC. Oral malodor of whole mouth, tongue, and saliva of the subjects was recorded by an experienced judge on a continuous 10-cm scale; peak and steady-state VSC intraoral levels were measured by the Interscan 1170 sulphide monitor. Log-transformed VSC and diamine levels were compared with odor judge measurements by Pearson analysis and stepwise forward multiple regression. Putrescine scores were not significantly associated with odor judge parameters or with VSC levels (p > 0.1). However, highly significant correlations (p ≤ 0.003) were found between cadaverine levels and all three...

Cadaverine as a Putative Component of Oral Malodor

The high affinity of Acinetobacter calcoaceticus RAG-1 for liquid hydrocarbons permitted the isolation of a spontaneous nonadherent mutant, MR-481. Strain MR-481 exhibited no significant affinity for three test hydrocarbons, yet resembled the wild type in many properties, including production of the extracellular emulsifying agent emulsan. To study the role of adherence in growth on hydrocarbons, RAG-1 and MR-481 were compared for growth on hexadecane under conditions of limited agitation and at low initial cell densities. Adherent RAG-1 cells were able to grow rapidly under these conditions, whereas nonadherent MR-481 cells failed to grow for at least 54 h. However, the addition of emulsan either initially or at various times after inoculation enabled the nonadherent MR-481 cells to grow on hexadecane. Growth was not the result of reversion of MR-481 from nonadherent to adherent cells. The data demonstrate that adherence is a crucial factor in the growth of A. calcoaceticus RAG-1 on hexadecane in the absence of extracellular emulsification of the substrate. Images

Role of adherence in growth of Acinetobacter calcoaceticus RAG-1 on hexadecane.

Acinetobacter calcoaceticus RAG-1, a hydrocarbon-degrading bacterium which adheres avidly to hydrocarbons and other hydrophobic surfaces, possesses numerous thin fimbriae (ca. 3.5-nm diameter) on the cell surface. MR-481, a nonadherent mutant of RAG-1 which is unable to grow on hexadecane under conditions of limited emulsification and low initial cell density, lacks these fimbriae. Prolonged incubation of MR-481 in hexadecane medium enriched for partial adherence revertants. The reappearance of thin fimbriae was observed in all such revertant strains. RAG-1 cells and partial revertant strains were agglutinated in the presence of antibody, whereas MR-481 cells were not. Another mutant, AB15, which was previously isolated on the basis of its nonagglutinability in the presence of antibody, also lacked thin fimbriae and was conditionally nonadherent. Furthermore, strain AB15 was unable to grow on hexadecane medium. Adherence of RAG-1 cells to hexadecane was considerably reduced after shearing treatment. The material removed from the cell surface by shearing of RAG-1 and the partial revertant strains yielded a single antigenic band in RAG-1 and partial revertant strains, as observed by crossed immunoelectrophoresis. This band was absent in both fimbriae-less mutants, MR-481 and AB15. The data demonstrate that the thin fimbriae of RAG-1 (i) are a major factor in adherence to polystyrene and hydrocarbon, (ii) may be crucial in enabling growth of cells on hexadecane, and (iii) constitute the major cell surface agglutinogen.

Role of Thin Fimbriae in Adherence and Growth of Acinetobacter calcoaceticus RAG-1 on Hexadecane

A simple replica method is described for the rapid identification of colonies of bacteria which adhere to polystyrene. A correlation was found between the adherence of bacterial strains to polystyrene and cell surface hydrophobicity, suggesting the use of this technique in screening for cell surface mutants and in the isolation of hydrophobic bacteria from nature.

Bacterial adherence to polystyrene: a replica method of screening for bacterial hydrophobicity.

The 0-5 organoleptic scale is used widely in breath research and in trials to measure the efficacy of anti-odor agents. However, the precise relationship between odor scores and gas concentrations of target odorants is unknown. The purpose of this study was to relate mean organoleptic scores from odor judges (n = 7) for pure odorants (n = 8) representative of those found in oral malodor. Judges used a common 0-5 scale to report the odor intensity of sample sets in random order of concentration. Regression analysis of data showed that odor score was proportional to the log concentration of odorant, and comparison of slopes showed H(2)S to be the most significant in terms of odor power. Detection thresholds (mol.dm(-3)) were: Skatole (7.2 x 10(-13)) < methylmercaptan (1.0 x 10(-11)) < trimethylamine (1.8 x 10(-11)) < isovalerate (1.8 x 10(-11)) < butyrate (2.3 x 10(-10)) < hydrogen sulphide (6.4 x 10(-10)) < putrescine (9.1 x 10(-10)) < dimethyl disulphide (5.9 x 10(-8)). The study demonstrates the exponential nature of the olfactory response and shows that any single compound's contribution to malodor depends on odor power and threshold in addition to concentration.

Mel Rosenberg

Papers

Cadaverine as a Putative Component of Oral Malodor

Role of adherence in growth of Acinetobacter calcoaceticus RAG-1 on hexadecane.

Role of Thin Fimbriae in Adherence and Growth of Acinetobacter calcoaceticus RAG-1 on Hexadecane

Bacterial adherence to polystyrene: a replica method of screening for bacterial hydrophobicity.

Study on the Organoleptic Intensity Scale for Measuring Oral Malodor