Kaarle J Parikka

Belgian Department of Defense · Research Laboratory

We conducted a study in which fifty hyperthermophilic methanogens, including the (hyper)thermophilic genera Methanothermus, Methanocaldococcus, Methanothermococcus, Methanotorris and Methanopyrus, originating from hydrothermal vents, have been screened for the presence of VLPs or viruses

The islands of The French Austral and Antarctic Territories are situated in the South Indian Ocean. Located on a geothermal hotspot, the St Paul Island is an extinct volcano, partially submerged in the sea, that harbors hot springs. These shallow submarine hot springs range between 75°C-85°C degrees in temperature and are of neutral pH (6-7). As th...

Studies investigating viral ecology have mainly been conducted in temperate marine and freshwater habitats. Fewer reports are available on the often less accessible “extreme environments” such as hot springs. This study investigated prokaryotic- and virus-like particles (VLP) associated to hot springs, themselves situated in cold environments of th...

This study investigated prokaryotic and virus-like particles (VLP) associated to hot springs, themselves situated in cold environments of the Southern Hemisphere (i.e. in the French Southern and Antarctic Lands). This was performed by examining their abundance in hot springs and surrounding temperate seawater using both epifluorescence microscopy (E...

In this chapter, we summarize and discuss methods used to study viral interactions in aquatic environments. These methods to assess interactions between viruses, hosts and the environment (including other viruses) are operationally separated into interactions at the molecular, single-cell, and community levels. Many of these methods benefit from th...

During the past 30 years, a vast amount of articles has been published on the importance - in terms of abundance, diversity and functional roles - of viruses inhabiting the aquatic world (either marine or freshwater), which include several excellent reviews. Our knowledge e.g. on the interactions of viruses with the living (organisms) and non-livin...

The discovery of the numerical importance of viruses in a variety of (aquatic) ecosystems has changed our perception of their importance in microbial processes. Bacteria and Archaea undoubtedly represent the most abundant cellular life forms on Earth and past estimates of viral numbers (represented mainly by viruses infecting prokaryotes) have indi...

Data from 210 articles and five unpublished studies were used for the meta-analysis. Articles were gathered using on-line databases (ScienceDirect, Wiley Online Library, Springer Link, PubMed and Google), using the keywords "virus-to-prokaryote ratio", "virus-to-bacterium ratio", "VPR", "VBR" and "viral abundance". Interesting reports were also fou...

The worldwide antibiotic crisis has led to a renewed interest in phage therapy. Since time immemorial phages control bacterial populations on Earth. Potent lytic phages against bacterial pathogens can be isolated from the environment or selected from a collection in a matter of days. In addition, phages have the capacity to rapidly overcome bacteri...

Les virus constituent les entites biologiques les plus abondantes et les plus diversifiees au sein de la biosphere [1] et l’on sait aujourd’hui combien leurs roles sont multiples. Cela est particulierement vrai pour les virus qui infectent les organismes unicellulaires. L’institut technologique de la ville de Zurich a accueilli le troisieme colloqu...

Marine Freshwater Our results confirm that VPR can be used as a proxy of interactions between viruses and prokaryotes. High VPR ratio are indicative of ongoing viral processes. The higher the VPR, the higher the prokaryotic mortality induced by viral lysis. This analysis also reveals that many factors hide behind this simple ratio of viral and host...

Synthèse Retour de Congrès

Les virus peuvent être retrouvés dans tous les écosystèmes où de la vie est présente. Ils constituent l’entité biologique la plus abondante de la biosphère. Si de nombreuses données sont disponibles sur l’abondance et la dynamique virale dans les écosystèmes aquatiques tempérés, peu d’études ont été menées sur ces aspects dans les milieux extrêmes,...

The abundances of the thermophilic microbial communities and the VLPs associated to them are: a prokaryotic abundance ranging from 0.07 x 106 to 6.7 x 106 cells/ml and a VLP abundance ranging from 0.04 x 106 to 2.2 x 106 VLPs/ml. These results are similar the data available today, indicating prokaryotic and VLP abundances of the order of 104 – 106...

The observations on each level (raw sample/enrichment culture/ isolates) reveal classical phage morphologies (belonging to Caudovirales) as well as a new type of phage morphology. The presence of vesicules, similar to those recently described by Soler et al * were also observed in both anaerobic enrichment cultures and archaeal isolates.

A novel temperate bacteriophage was isolated from a Bacillus cereus cereulide-producing strain and named vB_BceS-IEBH. vB_BceS-IEBH belongs to the Siphoviridae family. The complete genome sequence (53 kb) was determined and annotated. Eighty-seven ORFs were detected and for 28, a putative function was assigned using the ACLAME database. vB_BceS-IEB...