Bacteria plant root colonizing

Pseudomonas. These gram-aegative bacteria are a diverse group of microbes that iahabit plants, water, and sod. Pseudomonads are metabohcaHy versatile, capable of carrying out chemical transformations, mineralization of organic compounds, and colonization on plant roots (16). The use of Pseudomonads strains ia the clean up of chemical wastes and od spills has drawn considerable attention. 

In some cases pectinolytic enzymes have been associated with virulence and it is generally accepted that pectinolysis by these bacteria facilitates their entry and spread in plant tissue. In Rhizohium, these enzymes may play a role in the root infection process that precedes nodule formation (Hubbell et al 1978). A. irakense has never been reported to be pathogenic on plants. It can therefore be speculated that moderate and strictly regulated pectinolysis of A. irakense facilitates entry in the outer cortex of plants roots, since A. irakense has been isolated from surface-sterilized roots. It is likely that breakdown of plant polysaccharides by root colonizing bacteria can provide them with extra carbon source. 

Suslow, T.V. Role of root-colonizing bacteria in plant growth. In, Phytopathogenic Prokaryotes, Mount, M.S., Lacy, G.H. eds. Volume 1. Academic Press New York, 1982, pp. 187-223. 

A phenotypically similar type of resistance is observed following the colonization of plant roots by selected strains of non-padiogenic Pseudomonas Jluorescens bacteria. This type of Induced resistance is called rhizobacteria-mediated induced systemic resistance (ISR) [7]. 

In a system similar to the marine epibiontic bacteria, rhizobacteria appear to confer disease resistance to the host plants. For example, treatment of sugar beets with the rhizobacterium Pseudomonas in non-sterile soil has been shown to result in enhanced plant growth and severely reduced fungal root colonization (up to 62%) [143]. Rhizobacteria clearly may be sources of antifungal compounds for pharmaceutical or agricultural use. 

Although the family Leguminoseae includes tropical and temperate plants, most of these can be infected by bacteria of the Rhizobium spp, which colonize the plant roots within nodules. It has been estimated that root nodules may supplement soil N by more than 200 kg ha yr - under favourable... 

Iron uptake by bacteria at sites of lateral root emergence has been further confirmed using another technique employing 7-nitrobenz-2-oxa-l,3-diazole-desferrioxamine B, which is a derivitized siderophore that becomes fluorescent after it is deferrated (78). In this case, iron uptake from the siderophore ferrox-amine B was a.ssociated primarily with microbially colonized roots, but both plant and iron uptake from this chelate occurred in the regions just behind the root tips. 

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