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The hypothesis of the present study was that the termite mounds of Macrotermes subhyalinus (MS) (a litter–forager termite) were inhabited by a specific microflora that could enhance with the ectomycorrhizal fungal development. We tested the effect of this feeding group mound material on (i) the ectomycorrhization symbiosis between Acacia holosericea (an Australian Acacia introduced in the sahelian areas) and two ectomycorrhizal fungal isolates of Scleroderma dictyosporum (IR408 and IR412) in greenhouse conditions, (ii) the functional diversity of soil microflora and (iii) the diversity of fluorescent pseudomonads. The results showed that the termite mound amendment significantly increased the ectomycorrhizal expansion. MS mound amendment and ectomycorrhizal inoculation induced strong modifications of the soil functional microbial diversity by promoting the multiplication of carboxylic acid catabolizing microorganisms. The phylogenetic analysis showed that fluorescent pseudomonads mostly belong to the Pseudomonads monteillii species. One of these, P. monteillii isolate KR9, increased the ectomycorrhizal development between S. dictyosporum IR412 and A. holosericea. The occurrence of MS termite mounds could be involved in the expansion of ectomycorrhizal symbiosis and could be implicated in nutrient flow and local diversity. [ABSTRACT FROM AUTHOR]

Type three secretion systems (TTSSs) are protein translocation mechanisms associated with bacterial pathogenicity in host plants, and hypersensitive reactions in non-host plants. Distribution and diversity of TTSS-like genes within a collection of saprophytic and phytopathogenic fluorescent pseudomonads were characterized. This collection included 16 strains belonging to 13 pathogenic species, and 87 strains belonging to five saprophytic species isolated from plant rhizosphere and soil. Presence of conserved hypersensitive reaction/pathogenicity (hrp) genes (hrcRST) was assessed both by PCR using primers designed to amplify the corresponding sequence and by dot-blot hybridization using a PCR-amplified hrcRST fragment as a probe. PCR allowed the detection of TTSS-like genes in 75% and 32% of the phytopathogenic and saprophytic strains, respectively, and dot-blot hybridization in 100% and 49% of the phytopathogenic and saprophytic strains, respectively. The restriction fragment length polymorphism (RFLP) of 26 amplified hrcRST fragments revealed a considerable diversity. Twenty-one distinct RFLP types were identified and one hrcRST fragment was sequenced per RFLP type. The obtained hrcRST sequences clustered into three groups. Two of these groups included both phytopathogenic and saprophytic strains. The diversity of 16S rRNA genes, commonly used as an evolution marker, was characterized using PCR-RFLP. Polymorphism of the 16S rRNA genes corresponded to that of hrcRST genes, suggesting that these genes have followed a similar evolution. However, the occurrence of few mismatches suggests that sometimes TTSS-like genes might have undergone horizontal genetic transfer. [Copyright &y& Elsevier]