Lexikon

Gram-negative bacteria are those bacteria that do not retain crystal violet dye in the Gram staining protocol. The test itself is useful in classifying two distinct types of bacteria based on the structural differences of their cell walls. On the other hand, Gram-positive bacteria will retain the crystal violet dye when washed in a decolorizing solution.

The pathogenic capability of Gram-negative bacteria is often associated with certain components of Gram-negative cell walls, in particular, the lipopolysaccharide (also known as LPS or endotoxin) layer. In humans, LPS triggers an innate immune response characterized by cytokine production and immune system activation. Inflammation is a common result of cytokine production, which can also produce host toxicity. The human immun-response (and also the antibiotics) can be avoided by cell-wall mutation, which is a frequent process within Gram-negative bacteria, due to their complex cell-wall structure with proteins, lipoproteins and lipopolisaccharides.

The following characteristics are displayed by Gram-negative bacteria:

1. Cytoplasmic membrane
2. Thin peptidoglycan (murein) layer (which is much thinner than in Gram-positive bacteria)
3. Outer membrane containing lipopolysaccharide (LPS, which consists of lipid A, core polysaccharide, and O antigen) outside the peptidoglycan layer
4. Porins exist in the outer membrane, which act like pores for particular molecules
5. There is a space between the layers of peptidoglycan and the secondary cell membrane called the periplasmic space
6. The S-layer is directly attached to the outer membrane, rather than the peptidoglycan
7. If present, flagella have four supporting rings instead of two
8. No teichoic acids or lipoteichoic acids are present
9. Lipoproteins are attached to the polysaccharide backbone.
10. Most do not sporulate (Coxiella burnetii, which produces spore-like structures, is a notable exception)

The proteobacteria are a major group of Gram-negative bacteria, including Escherichia coli, Salmonella, Shigella, and other Enterobacteriaceae, Pseudomonas, Moraxella, Helicobacter, Stenotrophomonas, Bdellovibrio, acetic acid bacteria, Legionella and alpha-proteobacteria as Wolbachia and numerous others. Other notable groups of Gram-negative bacteria include the cyanobacteria, spirochaetes, green sulfur and green non-sulfur bacteria.

Medically relevant Gram-negative cocci include three organisms, which cause a sexually transmitted disease (Neisseria gonorrhoeae), a meningitis (Neisseria meningitidis), and respiratory symptoms (Moraxella catarrhalis).

Medically relevant Gram-negative bacilli include a multitude of species. Some of them primarily cause respiratory problems (Hemophilus influenzae, Klebsiella pneumoniae, Legionella pneumophila, Pseudomonas aeruginosa), primarily urinary problems (Escherichia coli, Proteus mirabilis, Enterobacter cloacae, Serratia marcescens), and primarily gastrointestinal problems (Helicobacter pylori, Salmonella enteritidis, Salmonella typhi).

Gram-negative bacteria associated with nosocomial infections include Acinetobacter baumannii, which cause bacteremia, secondary meningitis, and ventilator-associated pneumonia in intensive-care units of hospital establishments.

One of the several unique characteristics of Gram-negative bacteria is the structure of their outer membrane. The outer leaflet of the membrane comprises a complex lipopolysaccharide whose lipid portion acts as an endotoxin. If endotoxin enters the circulatory system, it causes a toxic reaction, with the sufferer's developing a high temperature, high respiration rate, and low blood pressure. This may lead to endotoxic shock, which may be fatal.

This outer membrane protects the bacteria from several antibiotics, dyes, and detergents that would normally damage the inner membrane or cell wall (peptidoglycan). The outer membrane provides these bacteria with resistance to lysozyme and penicillin. However, alternative medicinal treatments such as lysozyme with EDTA and the antibiotic ampicillin have been developed to combat the protective outer membrane of some pathogenic Gram-negative organisms. Other drugs can be used, significant ones being chloramphenicol, streptomycin, and nalidixic acid.

Source: http://en.wikipedia.org/wiki/Gram-negative_bacteria

granulometry (effective hydrodynamic radius, m): the parameter of interest for particle size distribution The particle size distribution is needed in order to decide which route of administration is most appropriate for animal toxicity studies (acute toxicity and repeated dose toxicity).

The different particle sizes defined in EN 481 document1 are:

· inhalable fraction: mass fraction of particles that can be inhaled by nose and mouth;

· thoracic fraction: mass fraction of particles that passes the larynx;

· respirable fraction: mass fraction of particles that reaches the alveoli.

The determination of the particle size fractions is used to assess the possible health effects resulting from inhalation of airborne particles in the workplace.

Greenpeace's cornerstone principles and core values are reflected in all our environmental campaign work, worldwide. These are:

• "Bearing witness" to environmental destruction in a peaceful, non-violent manner;
• Using non-violent confrontation to raise the level and quality of public debate;
• In exposing threats to the environment and finding solutions they have no permanent allies or adversaries;
• Ensuring financial independence from political or commercial interests;
• Seeking solutions for, and promote open, informed debate about society's environmental choices.

http://www.greenpeace.org/international/en/

GRO range consists of hydrocarbons containing between 6 and 12 carbon atoms and includes aromatic compounds, alkanes, cycloalkanes and branched alkanes. Approximately 40% of the hydrocarbons in fresh petrol are monoaromatic compounds such as benzene, toluene and ethylbenzene (BTEX). The sum of GRO and DRO gives TPH.

all water which is below the surface of the ground in the saturation zone and in direct contact with the ground or subsoil.

groundwater protection describes the management processes by which groundwater quality and resources are protected against pollution and over-exploitation. (Source: EUGRIS)

available groundwater resource is the long-term annual average rate of overall recharge of the body of groundwater less the long-term annual rate of flow required to achieve the ecological quality objectives for associated surface waters, to avoid any significant diminution in the ecological status of such waters and to avoid any significant damage to associated terrestrial ecosystems.

"groundwater status" is the general expression of the status of a body of groundwater, determined by the poorer of its quantitative status and its chemical status.

"good groundwater chemical status" is the chemical status of a body of groundwater, which meets all the conditions set out in table 2.3.2 of Annex V of Water Framework Directive (60/2000/EC).

is an expression of the degree to which a body of groundwater is affected by direct and indirect abstractions.