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philpense 02-28-2014 05:02 AM

Epiphyte Microbes
 
Have a background in biology but from many years ago. Looking to work with a microbe epiphyte like Pseudomonas Fluorescans. It has some pathogenicity with immunocompromised individuals. Is there any established scientific discipline that seeks to interfere with if not neuter a microbes abiliity to infect. Guidance sought

cusabio1 03-03-2014 07:34 AM

Re: Epiphyte Microbes
 
Pseudomonas fluorescens is a common Gram-negative, rod-shaped bacterium.It belongs to the Pseudomonas genus; 16S rRNA analysis has placed P. fluorescens in the P. fluorescens group within the genus,to which it lends its name.P. fluorescens has multiple flagella. It has an extremely versatile metabolism, and can be found in the soil and in water. It is an obligate aerobe, but certain strains are capable of using nitrate instead of oxygen as a final electron acceptor during cellular respiration.Optimal temperatures for growth of Pseudomonas fluorescens are 25-30 degrees Celsius. It tests positive for the oxidase test. Pseudomonas fluorescens is also a nonsaccharolytic bacteria.Heat-stable lipases and proteases are produced by Pseudomonas fluorescens and other similar pseudomonads.These enzymes cause milk to spoil, by causing bitterness, casein breakdown, and ropiness due to production of slime and coagulation of proteins.

It is not clear exactly how the plant growth-promoting properties of P. fluorescens are achieved; theories include:

the bacteria might induce systemic resistance in the host plant, so it can better resist attack by a true pathogen
the bacteria might outcompete other (pathogenic) soil microbes, e.g., by siderophores, giving a competitive advantage at scavenging for iron
the bacteria might produce compounds antagonistic to other soil microbes, such as phenazine-type antibiotics or hydrogen cyanide

To be specific, certain P. fluorescens isolates produce the secondary metabolite 2,4-diacetylphloroglucinol, the compound found to be responsible for antiphytopathogenic and biocontrol properties in these strains.The phl gene cluster encodes factors for 2,4-DAPG biosynthesis, regulation, export, and degradation. Eight genes, phlHGFACBDE, are annotated in this cluster and conserved organizationally in 2,4-DAPG-producing strains of P. fluorescens. Of these genes, phlD encodes a type III polyketide synthase, representing the key biosynthetic factor for 2,4-DAPG production. PhlD shows similarity to plant chalcone synthases and has been theorized to originate from horizontal gene transfer.But phylogenetic and genomic analysis has revealed that the entire phl gene cluster is ancestral to P. fluorescens, many strains have lost the capacity, and it exists on different genomic regions among strains.

There is experimental evidence to support all of these theories, in certain conditions; a good review of the topic is written by Haas and Defago.

The strain referred to as Pf-CL145A has proved itself a promising solution to the invasive Dreissena (zebra and quagga) mussels. The strain of the bacteria produces toxins that destroy the digestive system of the mussels and produces a >90% kill rate.

Several strains of "P. Fluorescens", such as Pf-5 and JL3985, have developed a natural resistance to ampicillin and streptomycin. These antibiotics are regularly used in biological research as a selective pressure tool to promote plasmid expression.


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