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A morphological and molecular study shows that the arbuscular-mycorrhizal fungus, Gigaspora margarita, harbors a large homogeneous population of a bacterial endosymbiont within its cytoplasm. The endosymbiont occurs at all stages of the fungal life-cycle. There are about 250,000 live bacteria in each fungal spore. The bacterial endosymbiont is an rRNA group II pseudomonad of the genus Burkholderia. They are viable, and multiply and travel from the spores to the root of the host fungus through the mycelium.

Information about acetic acid bacteria (AAB) recovered from insects is provided. The close association of AAB and their insect hosts is confirmed by the multiple modes of transmission between individuals and to their progeny, thus indicating that AAB has represented novel secondary symbionts of insects.

The detection of acetic acid bacteria (AAB) of the genus Asaia as symbionts of mosquitoes has helped in examining the diversity of the symbionts and their relationships in different mosquito species and populations. The Asaia isolates are typed by internal transcribed spacer (ITS)-PCR, tRNA-PCR, BOX-PCR, and randomly amplified polymorphic DNA (RAPD)-PCR, which have shown that different Asaia strains are present in different mosquito populations and even in single individuals.

Cultivation-dependent and -independent methods are used for examining the microbiota associated with Bactrocera oleae, one of the agricultural pests in olive-producing countries. A strain labeled with a green fluorescent protein is used for showing the capability to colonize and lodge in the digestive system of both larvae and adults and in malpighian tubules of adults.

Flavescence doree, is a grapevine disease caused by the bacterium 'Candidatus Phytoplasma vitis' and spread throughout the vineyards by a leafhopper, Scaphoideus titanus. A survey was conducted to characterize the bacterial microflora associated with S. titanus using length heterogeneity PCR and the results reveal that this endosymbiont and 'Ca. Phytoplasma vitis' have a partially overlapping colonization pathway in the insect body, colocalizing in the fat body and salivary glands.

An intracellular bacterium from ixodes ricnus ticks collected in Italy is characterized by electron microscopy (EM), PCR sequencing of the 16S rRNA gene, molecular phylogenetic analysis, and in situ hybridization (ISH). In spite of the apparent parasitism of host mitochondria by IricESI, the available information suggests that the bacterium has an obligate relationship with its host, although this is not yet confirmed.

An intracellular bacterium from Ixodes ricinus ticks collected in Italy was characterized by electron microscopy (EM), PCR sequencing of the 16S rRNA gene, molecular phylogenetic analysis, and in situ hybridization (ISH). This bacterium was shown by EM to be present in the cytoplasm, as well as in the mitochondria of ovarian cells. When universal 16S rRNA bacterial primers were used, PCR amplification of ovarian DNA followed by cloning and sequencing resulted in the same sequence being found in each sample. Phylogenetic analysis of this sequence showed that the bacterium from which it was derived, tentatively designated IricES1, is part of a novel clade in the alpha subdivision of the Proteobacterium: ISH and PCR assays of various tissues performed with oligonucleotides specific for the IricES1 16S rRNA showed that IricES1 is restricted to ovarian cells. Based on the results obtained, we inferred that the bacteria seen by EM in ovarian cells are a single type of bacteria, corresponding to IricES1. PCR screening of 166 ticks from various parts of Italy and one site in England showed that IricES1 was present in 96% of adult females and 44% of nymphs (unsexed). No adult males were found to be infected. Despite the apparent parasitism of host mitochondria by IricES1, the available information suggests that the bacterium has an obligate relationship with its host, although this must be confirmed.