Journal of Microbiology

Volume 53(3); March 2015

Reviews

Counts and sequences, observations that continue to change our understanding of viruses in nature: K. Eric Wommack , Daniel J. Nasko , Jessica Chopyk , Eric G. Sakowski; J. Microbiol. 2015;53(3):181-192. Published online March 3, 2015; DOI: https://doi.org/10.1007/s12275-015-5068-6

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52 Citations

Abstract: The discovery of abundant viruses in the oceans and on land has ushered in a quarter century of groundbreaking advancements in our understanding of viruses within ecosystems. Two types of observations from environmental samples - direct counts of viral particles and viral metagenomic sequences - have been critical to these discoveries. Accurate direct counts have established ecosystem-scale trends in the impacts of viral infection on microbial host populations and have shown that viral communities within aquatic and soil environments respond to both short term and seasonal environmental change. Direct counts have been critical for estimating viral production rate, a measurement essential to quantifying the implications of viral infection for the biogeochemical cycling of nutrients within ecosystems. While direct counts have defined the magnitude of viral processes; shotgun sequences of environmental viral DNA - virome sequences - have enabled researchers to estimate the diversity and composition of natural viral communities. Virome-enabled studies have found the virioplankton to contain thousands of viral genotypes in communities where the most dominant viral population accounts for a small fraction of total abundance followed by a long tail of diverse populations. Detailed examination of long virome sequences has led to new understanding of genotype-to-phenotype connections within marine viruses and revealed that viruses carry metabolic genes that are important to maintaining cellular energy during viral replication. Increased access to long virome sequences will undoubtedly reveal more genetic secrets of viruses and enable us to build a genomics rulebook for predicting key biological and ecological features of unknown viruses.

Microbial ecology in Hydra: Why viruses matter: Thomas C.G. Bosch , Juris A. Grasis , Tim Lachnit; J. Microbiol. 2015;53(3):193-200. Published online March 3, 2015; DOI: https://doi.org/10.1007/s12275-015-4695-2

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19 Citations

Abstract: While largely studied because of their harmful effects on human health, there is growing appreciation that viruses are also important members of the animal holobiont. This review highlights recent findings on viruses associated with Hydra and related Cnidaria. These early evolutionary diverging animals not only select their bacterial communities but also select for viral communities in a species-specific manner. The majority of the viruses associating with these animals are bacteriophages. We demonstrate that the animal host and its virome have evolved into a homeostatic, symbiotic relationship and propose that viruses are an important part of the Hydra holobiont by controlling the species-specific microbiome. We conclude that beneficial virus-bacterial-host interactions should be considered as an integral part of animal development and evolution.

Against friend and foe: Type 6 effectors in plant-associated bacteria: Choong-Min Ryu; J. Microbiol. 2015;53(3):201-208. Published online March 3, 2015; DOI: https://doi.org/10.1007/s12275-015-5055-y

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31 Citations

Abstract: Bacterial secretion systems play critical roles in communication with neighboring bacteria and in the modulation of host immune responses via the secretion of small proteins called effectors. Several secretion systems have been identified and these are denoted types I-II. Of these, the type VI secretion system (T6SS) and its effectors were only recently elucidated. Most studies on the role and significance of the T6SS and its effectors have focused on human pathogens. In this review, type 6 effectors from plant-associated beneficial and pathogenic bacteria are discussed, including effectors from Agrobacterium tumefaciens, Dickeya dadanti, Rhizobium leguminosarum, Pectobacterium atroseptium, Ralstonia solanacearum, Pseudomonas syringae, Pseudomonas fluorescens, and Pseudomonas protegens. Type 6 effectors act in symbiosis, biofilm formation, virulence, and interbacterial competition. Understanding the impact of type 6 effectors on pathogenesis will contribute to the management of bacterial pathogens in crop plants by allowing the manipulation of intra and inter-specific interactions.

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