Bacterial biofilms are communities of microorganisms residing within a polysaccharide matrix. Dental plaque, slimy coating in tanks, and algal mats on bodies of water are examples of biofilms. It is well accepted that biofilms play important role in bacterial persistence and antibiotic resistance in chronic infections. It is acknowledged that the majority of microbial cells on earth are living in distinct communities as biofilms. In fact, it is now known that 99% of all bacteria exist in biofilms, with only 1% living in the planktonic state. It has been estimated that 65% of microbial infections are associated with biofilms which constitute a microbial multicellular lifestyle and are defined as organized communities of bacteria. The structural nature of biofilms can protect the cells against antimicrobial agents and the host's defense. The microbial community inside a biofilm can also be protected against adverse conditions such as desiccation, osmotic shock, UV radiation, or exposure to toxic compounds, or predators. Due to the heterogeneous nature of biofilms, it is likely that multiple mechanisms of antimicrobial resistance can occur.

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Background: Microbial cultures are extensively used as environment friendly ways for biological control of parasitic pests, including the root-knot nematodes, alternative to the use of chemical nematicides. The present study was conducted to isolate some lytic rhizobacteria and examine their nematicidal activity against Meloidogyne incognita J 2 mortality and egg hatching in in vitro test. Results: Lytic Rhizobacteria were isolated from soil samples adhering to tomato plant roots from different localities at Giza governorate, Egypt. Six bacterial isolates, exhibited high efficacy against root-knot nematodes, were identified based on the analysis of the 16S rRNA gene sequence as Pseudomonas aeruginosa, Paenibacillus polymyxa, Lysinibacillus sphaericus, Bacillus cereus, Bacillus subtilis, and Achromobacter xylosoxidans. These strains showed high production of chitinase, chitosanase, and protease using colloidal chitin and soluble chitosan as carbon sources. Two strains, Paenibacillus polymyxa and Bacillus subtilis, produced the highest levels of chitinase in the media. Except for Pseudomonas aeruginosa, all the bacterial strains produced high levels of chitosanase. Conclusion: The results revealed that high amounts of protease were, however, secreted by Pseudomonas aeruginosa as compared to the other strains. In in vitro tests, all the bacterial culture filtrates potentially displayed nematicidal effect in M. incognita egg hatching and an obvious increase in J 2 mortality as compared to control. Paenibacillus polymyxa caused 100% juvenile mortality followed by Bacillus subtilis 97.25%, Bacillus cereus 94%, Achromobacter xylosoxidans 93%, Lysinibacillus sphaericus 92%, and Pseudomonas aeruginosa 84.29% after 48 h of exposure, as compared to control.

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