To understand the factors governing the diversity, abundance and host associations of parasitoids attacking frugivorous drosophilid flies on Iriomote-jima, a subtropical island of Japan, we monitored parasitism on several occasions over the period 2003–2009. Fifteen drosophilid and 12 parasitoid species were recorded. Three species of Drosophila, D. bipectinata, D. albomicans and D. takahashii, bred abundantly in banana baits, though their abundance varied between years and seasons. Frequent parasitoid species were Asobara japonica, A. pleuralis (Braconidae), Leptopilina ryukyuensis and L. pacifica (Figitidae). L. victoriae was recorded only in December 2003. In addition, host acceptance and host suitability of the four most frequently recorded parasitoid species were studied in the laboratory. Most parasitoid and drosophilid species showed species-specific associations with more than one antagonist species, suggesting that they have been subjected to complex coevolutionary interactions. In addition, host range of most of the parasitoid species included one of the three major Drosophila species, suggesting that the abundance of potential hosts is one of the factors determining the evolution of parasitoid host use., Biljan Novkovic ... [et al.]., and Obsahuje seznam literatury
The mechanisms which permit Leishmania to survive inside macrophages are not totally understood although it is known that prolonged culture in vitro results in loss of virulence. One of the cell surface molecules often implicated in virulence mechanisms is the glycoprotein of 63 kDa (gp63). In this work we studied changes in infectivity of L. infantum promastigotes maintained in vitro by subcultures, correlated with the proteolytic activity of gp63. It was observed that L. infantum MON-1 promastigotes became unable to establish an infection after 6 subcultures in vitro independently of the size of inoculum. This corresponded to a diminution of proteolytic activity of gp63. L infantum MON-1 promastigotes inoculated in hamsters viscera-lize in the mononuclear phagocytic system accompanied by an antibody response. A correlation between antibody response, inoculum size and promasti gote origin was verified. L donovani MON-18 and L. infantum MON-24 promastigotes produced a specific humoral response but failed to establish an infection in hamsters regardless of all the passages tested.
Laboratory animals (mice and guinea pigs) were infected with the isolates of Coxiella burnetii (Derrick, 1939) obtained from bovine milk (M18 and M35) and the ticks Ixodes ricinus (Linnaeus, 1758) and Dermacentor marginatus (Sulzer, 1776) (Kl3 and Kl6, respectively), and with the reference strain Nine Mile. Neither mortality nor lethality occurred with the mice. Antibody response in mice infected with isolates from milk was lower (1 : 16-512) than that from ticks (1 : 32-4096). Onset of seropositivity also occurred later - on the 10th day post-infection (p.i.) for M18 and M35 in comparison with the 7th day for Kl3 and Kl6. In guinea pigs, infection manifested by fever. The fever was less evident in guinea pigs infected with isolates from milk (39.5-40.1°C) than in guinea pigs infected with isolates from ticks (39.5-40.6°C). Partially engorged females of Dermacentor reticulatus (Fabricius, 1794) were inoculated with isolates M18 and Kl3 . No differences in the multiplication of C. burnetii in haemocytes between these two isolates were ascertained.
The most recent genome-editing system called CRISPR-Cas9 (clustered regularly interspaced short palindromic repeat system with associated protein 9-nuclease) was employed to delete four non-essential genes (i.e., Caeco1, Caidh1, Carom2, and Cataf10) individually to establish their gene functionality annotations in pathogen Candida albicans. The biological roles of these genes were investigated with respect to the cell wall integrity and biogenesis, calcium/calcineurin pathways, susceptibility of mutants towards temperature, drugs and salts. All the mutants showed increased vulnerability compared to the wild-type background strain towards the cell wall-perturbing agents, (antifungal) drugs and salts. All the mutants also exhibited repressed and defective hyphal growth and smaller colony size than control CA14. The cell cycle of all the mutants decreased enormously except for those with Carom2 deletion. The budding index and budding size also increased for all mutants with altered bud shape. The disposition of the mutants towards cell wall-perturbing enzymes disclosed lower survival and more rapid cell wall lysis events than in wild types. The pathogenicity and virulence of the mutants was checked by adhesion assay, and strains lacking rom2 and eco1 were found to possess the least adhesion capacity, which is synonymous to their decreased pathogenicity and virulence.
Systemic ciliatosis caused by histophagous ciliates constitutes a serious disease of cultured turbot. Six ciliate isolates were obtained from parasitized turbot during six epizootics at four different farms located in Spain, France and Portugal. Axenic cultures of the six isolates were obtained by periodical subculturing in ATCC 1651MA or supplemented L-15 media. In basal media or seawater, the parasites could survive starving for long periods with no apparent proliferation. In adequate media, growth kinetics was found to be very similar for isolates A and B, with a clear influence of temperature. Morphological studies demonstrated that all isolates share common features that allows their assignment to either Philasterides Kahl, 1931 or Miamiensis Thompson et Moewus, 1964. However, statistically significant differences were evident in pairwise comparisons of the isolates from the four farm sites in 16 taxonomically relevant morphometric features. This could allow the discrimination of different species or strains. Virulence of isolates A and B for healthy turbot was tested in several experiments. Differences in the virulence were especially evident after long-term in vitro culturing, isolate A being clearly attenuated after 35-42 passages, whereas isolate B became more virulent after 20-42 passages. The need of further studies to confirm such virulence variability and its implications in pathogenesis and prevention of turbot scuticociliatoses is stressed.
It has been reported that the virulence of axenically cultivated Entamoeba histolytica increases following growth with cholesterol. The purpose of this study was to determine whether cholesterol would enhance the virulence of axenically cultivated Naegleria fowleri. Amoebae were cultivated in axenic medium with (100 pg/ml) or without cholesterol for 6 months and tested in mice for changes in virulence. After 6 months of continuous cultivation, N. fowleri grown with cholesterol was less virulent for mice than the same strain grown without cholesterol.
This is a followup report on the viability of pathogenic Acanthamoeba castellami, Naegleria australiensis, and N. fowleri during 5 years of cryopreservation and the virulence of N. fowleri during 30 months of cryostorage, all at -70’C. The greatest decrease in viability occurred during the first year of freezing and was 10-fold greater than the average yearly decrease during years 2-5. At 5 years of cryostorage, viability was 33 % for A. castellana, 38 % for N. fowleri and 51% for N. australiensis. Virulence of N. fowleri did not decrease during 30 months of freezing and what appeared to be an increase in virulence during cryopreservation may be the result of reduced viability of the less virulent amebae in a culture.
The Leishmania metalloproteinase GP63 has been reported to play important roles mainly in resistance of promastigotes to complement-mediated lysis and in interaction with macrophage receptors. On the other hand, its function in insect vectors is still unclear. We compared the structure and dosage of gp63 genes and the activity of GP63 in Leishmania major Yakimoff et Schokhor strains and lines differing in virulence for mice and ability to develop in sand flies. The results demonstrate considerable variability in amount and proteolytical activity of GP63 among L. major strains although genomic changes in the gp63 locus were not found. Attenuated LV561/AV line showed low amount and low enzymatic activity of GP63. Serial passages of attenuated parasites through either Phlebotomus duboscqi Neveu-Lemaire or through mice led to a recovery of GP63 proteolytical activity to the level present in virulent LV561/V line. Overexpression of GP63 was found in two L. major strains (L119, Neal) with defective lipophosphoglycan (LPG); both these strains were capable to cause mice infection but unable to survive and multiply in sand flies. Differences were found also in karyotypes and in amount of minichromosomes amplified in some lines of the LV561 strain. The results suggest that parasite virulence is not simply correlated with the activity of GP63; however, this enzyme plays a significant role in association with other surface molecules, especially LPG. Overexpression of GP63 can compensate LPG defect in the vertebrate host but in sand flies both molecules fulfil quite different functions and the defect in LPG is lethal for the parasite. On the other hand, linear minichromosomes of about 200 kb found in some lines of the LV561 strain are associated with development in vitro and in the vector but they are not essential for the infection of the vertebrate host.