Two Mimivirus-like giant viruses were isolated independently from each other from the same plane tree (Platanus occidentalis). The first isolate KSL5 was discovered within its natural host Saccamoeba strain SL5 and was associated with a small icosahedral satellite virus. The phylogenetic analysis of the host amoeba revealed a close relatedness of the 18S rRNA gene to Saccamoeba lacustris. The second giant virus KSL5x was isolated using the virus free S. lacustris strain SL5 as bait. Interestingly KSL5x did not show any affiliation with a satellite virus. Association experiments of the satellite virus with the KSL5x infected host cells resulted in a co-infection of the S. lacustris strain SL5 indicating that the satellite virus could multiply in coexistence with giant virus KSL5x as well. However challenging S. lacustris SL5 with only the satellite virus did not lead to any visible infection of the host cells or the multiplication of the virus. We therefore conclude a strong dependency of the satellite virus on the virus factory of KSL5. Evaluations of the host range of KSL5 showed that only two of three S. lacustris strains were susceptible to the new giant virus KSL5 indicating a highly species-specific virus-virophage system in S. lacustris. As suggested by Hauroder et al. (2017) we propose the name Platanovirus saccamoebae for the new Mimivirus-like giant virus KSL5.
This work investigated the microbial content of decaying nodules from alders. The 16S rDNA composition of the microbiome of six senescent alder nodules was investigated by 454 sequencing. All nodules still had some Frankia sequences present, but in each case it was only detected at minor levels, with other organisms predominating. Although organisms from three different phyla (Bacteroidetes, Proteobacteria and Actinobacteria) constituted almost all (98% or more) of all sequences, Bacteroidetes were most abundant in four nodules with Proteobacteria being most abundant in the other two. In addition a few families were represented at a level of 10% or more of the total sequences: Sphingobacteriaceae (all 6 nodules); Chitinophagaceae (5 of 6); non-Frankia Actinomycetales (2 of 6); Caulobacteraceae (2 of 6); Flavobacteriaceae (2 of 6); Oxalobacteraceae (1 of 6); and Xanthomoadaceae (1 of 6). Analysis at the genus level showed a diverse range of organisms, with members of the genus Pedobacter being found at an abundant level within most nodules.
CurT represents a cyanobacterial homolog of the Arabidopsis CURVATURE THYLAKOID1 protein family, which is involved in grana formation in chloroplasts. Inactivation of the curT gene has recently been shown to cause severe alterations of the thylakoid membrane architecture affecting in particular PSII biogenesis. The CurT protein localized with high local abundances in regions, where the thylakoids converge towards the plasma membrane. Interestingly, CurT relocalized to the plasma membrane under salt and osmotic stress. Consistent with a potential role of this protein during stress response, the curT- mutant exhibited a high sensitivity towards both high exogenous salt and osmotic concentrations. This study demonstrates that curT- is still able to accumulate compatible solutes in amounts and dynamics similar to wild-type cells. In conclusion, accumulation of compatible solutes is not sufficient to provide protection from osmotic stress. Moreover, CurT-dependent membrane stabilization appears to be required to enable cells to resist high levels of osmotic stress.
A method is described which allows isolation of macronuclear DNA from the rumen ciliate Entodinium caudatum. Ciliate cells were enriched from the total microbial population in the rumen of sheep with a single ciliate species present by sedimentation and size filtration. Ciliates were then lysed by homogenisation and the macronuclear component isolated on a Percoll density gradient. Macronuclei can be stored in guanidine. HCl until ready for DNA extraction. DNA which had been extracted from macronuclei fresh from the Percoll gradient, or following guanidine. HCl storage, is of sufficient quality to permit its use for PCR analysis.
This work investigated the microbial content of nodules from alders to determine how many ribotypes of Frankia were present and which, if any, other bacteria existed within nodes from the nodules. The bacterial content of alder nodules was investigated by 454 sequencing of 16S rDNA genes. Over half of the sequences were from a single ribotype of Frankia, with nearly all other sequences coming from the chloroplast of the host plant, and other sequences (including other ribotypes of Frankia) being at < 1%. It is concluded that a single ribotype of Frankia is the major, although not unique, bacterium present in an individual lobe from an alder nodule.
Plants attract insects as pollinators but at the same time suf-fer damage from the same insect species, especially during their larval stages. To defend against herbivore attack, plants have evolved efficient defense and tolerance strategies, such as producing toxic chemicals, emitting volatiles to attract predators, and transferring nutrients to roots so as to better tolerate herbivore attack (Pare and Tumlinson 1999; Schwachtje and Baldwin 2008; Schuman et al. 2012.)Changes in gene regulation play essential roles in all of these defense responses.
Green hydra (Hydra viridissima Pallas, 1766) is a clas sical example of endosymbiosis. Described ultrastruc tural features of green hydra symbiosis are extensive widening of perialgal spaces, degradation, loss and fusion of symbiosomes. These changes are considered as defensive and protective mechanisms and the endo symbionts show greater viability than their host. Also, a certain degree of independency was noticed and for the first time endosymbiotic algae from green hydra have been successfully isolated and permanently main tained in pure lab culture. Microscopical and molecular analyses of the isolated endosymbionts resulted in the discovery of two hitherto undescribed endosymbiotic species in green hydra. In final conclusion, endosymbi otic algae from green hydra perform as the “stronger” symbiotic partner in green hydra symbiosis. We keep on searching for more evidence and results.
Almost all plants live in interactions with fungi, where they express different lifestyles ranging from mutualism (beneficial for both partners) through commensalism (beneficial for the microbe, while the host species is neither positively nor negatively affected) to parasitism (the host is noticeably harmed or deprived at the expense of the fungus). Mutualism represents a balanced stage of plant/microbe interactions. However, depending on the partner combination, the genetic constitutions of both partners, the developmental stage and the life-history of the symbiosis, the physiological status of both partners, the colonization pattern of the host, the ability of the microbe to produce toxins and of the host to defend them, the evolutionary status of the symbiosis, environmental and habitat-specific conditions and the stress situation, a mutualistic inter-action can become unstable and shift towards commensalism or parasitism. Genetic studies with mycorrhizal and endophytic fungi discovered genes which are crucial for determining a beneficial symbiotic stage. Recent progress in this field is summarized in this review. In addition, the interaction of the endophytic fungus Piriformospora indica with Arabidopsis as a novel model system in this field is introduced.
A coccoid endosymbiont was recovered from Hartmannella vermiformis OS101. The organism could be propagated in BGM and Vero cell cultures, was resistant to penicillin and exhibited structural characteristics comparable with Chlamydia spp. PCR using Chlamydia ompA gene and Coxiella-specific primers showed that the agent was distinct from chlamydiae or coxiellae. Determination of 16S ribosomal RNA signature sequences in combination with the morphological and developmental characteristics provided evidence that the isolate can be classified as Simkania negevensis or a closely related organism. Even the investigated signature sequences showed a high homology to those of the type strain of Simkania negevensis, its biological properties in amoebae cultures differed to that of strain Z.
It is highly possible that color mutants of Arabidopsis have abnormalities in chlorophyll biosynthesis steps or in the development of chloroplasts, where chlorophyll is accumulated. In this aspect, we are collecting and analyzing color mutants of Arabidopsis to study the biogenesis of chloroplasts. We screened seedlings from 35,000 ethyl methanesulfonate (EMS) mutagenized seeds of M2 generation with an average germination ratio of 47.7 %. Theoretically reached saturated mutagenesis, out of the mutant library we found 77 color mutant lines and characterized them. We found, by means of the quantification of chlorophyll content, that five lines showed a specific reduction of chlorophyll b content but not chlorophyll a content. A similar phenotype was reported with other lines carrying a mutation in the gene coding for chlorophyllide a oxygenase (CAO), which catalyzes the conversion of chlorophyll a to chlorophyll b. Complementation test was carried out by crossing all five lines with each other. Results indicate that mutations in at least two loci caused reduction of chlorophyll b content. One turned out to be a CAO mutation as determined using both chromosome mapping and complementation test with an established CAO mutant. The other was located near 35 cM of the 5th chromosome and was considered to be a novel mutation.
s The translation systems of animal mitochondria are known to utilize extremely simpli- fied tRNAs and rRNAs compared to the canonical translation systems of bacteria. It seems that the deficit in mitochondrial systems has been accommodated by the selection for novel proteins and/or enlarged bacterial homologues with longer N- or C- terminal regions that compensate for the missing regions in animal mitochondrial RNAs. On the basis of our previous studies, we discuss the possibility that certain structures and functions of bacterial RNAs were transferred to proteins during the evolutionary process from ancestral to extant organisms. Our analyses may provide appropriate mod- els for an experimental verification of the concept of transition from the RNA world to the RNP world in the early process of the evolution of life.
An aerobic, heterotrophic bacterium, termed strain APG1, was isolated from surfacesterilized fronds of Azolla pinnata, a water fern having symbiotic leaf cavities. Based on its fatty acid profile, morphology and biochemical characteristics, strain APG1 was assigned to the genus Rhodococcus. Exposure to light caused colonies to yellow due to accumulation of a s-carotene-like pigment. We suggest that photocarotenogenesis and other traits of strain APG1 could facilitate the survival of the bacterium in planta.
Endosymbiotic zooxanthellae, referred to Symbiodinium microadriaticum, are described in the non-bioeroding sponge Cinachyra tarentina Pulitzer-Finali,1983, by both light and transmission electron microscopy. The algae are intracellular, included in individual vacuoles of mesohyl cells, inside which they were observed in division. More than one zooxanthella may live in a sponge cell. The zooxanthellae measured about 8-9 mu m in diameter. No difference in their diameter was detected in relation to the location in the sponge body. Monthly sponge samplings over one year (from January to December 1996), allowed the presence/absence of the zooxanthellae to be ascertained. A total of 139 sponges were examined, the majority of which (112 specimens) harboured symbionts. The number of sponges lacking zooxanthellae progressively decreased with the approach of summer. From August to October all the specimens contained zooxanthellae. Typically, zooxanthellae have been recorded in clionids and their presence has generally been correlated with the boring activity and growth of these sponges. The present report shows no evidence of constraints in the evolution of the association between sponges and zooxanthellae along with a possible non-vertical transfer of symbionts to the new generations.
X-Bacteria, obligatory endosymbionts in the xD strain of Amoeba proteus, contain a macrophage infectivity potentiator (Mip)-like protein. We detected a 30-kDa Mip-like protein (Mipx) in X-bacteria by immunoblotting using an antibody against Mip of Legionella pneumophila as a probe. Using conserved nucleotide sequences from Legionella mip genes as primers, we obtained PCR products containing mip-like gene (mipx) from a genomic expression library of X-bacteria. We confirmed the presence of mipx in the genomic DNA of X-bacteria by Southern hybridization using a P-32-labeled PCR fragment as a probe. The mipx gene had a sequence identity of 79% and 74% with genes of Legionella micdadei and L. pneumophila, respectively. Mipx protein contained amino acids corresponding to the peptidyl-prolyl cis-trans isomerase (PPIase) activity region at its C-terminus. Recombinant Mipx protein produced by E. coli transformed with mipx exhibited the PPIase enzyme activity and the activity was inhibited by immunosuppressive drug, FK506. When X-bacteria were pretreated with FK506, X-bacteria's infectivity in amoebae was reduced to one-third that of the control group, and the results suggested that Mipx is involved in the initial infection of X-bacteria in amoebae.
