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Halobacteriovorax, an underestimated predator on bacteria: potential impact relative to viruses on bacterial mortality.

ABSTRACT: Predation on bacteria and accompanying mortality are important mechanisms in controlling bacterial populations and recycling of nutrients through the microbial loop. The agents most investigated and seen as responsible for bacterial mortality are viruses and protists. However, a body of evidence suggests that predatory bacteria such as the Halobacteriovorax (formerly Bacteriovorax), a Bdellovibrio-like organism, contribute substantially to bacterial death. Until now, conclusive evidence has been lacking. The goal of this study was to better understand the contributors to bacterial mortality by addressing the poorly understood role of Halobacteriovorax and how their role compares with that of viruses. The results revealed that when a concentrated suspension of Vibrio parahaemolyticus was added into microcosms of estuarine waters, the native Halobacteriovorax were the predators that responded first and most rapidly. Their numbers increased by four orders of magnitude, whereas V. parahaemolyticus prey numbers decreased by three orders of magnitude. In contrast, the extant virus population showed little increase and produced little change in the prey density. An independent experiment with stable isotope probing confirmed that Halobacteriovorax were the predators primarily responsible for the mortality of the V. parahaemolyticus. The results show that Halobacteriovorax have the potential to be significant contributors to bacterial mortality, and in such cases, predation by Halobacteriovorax may be an important mechanism of nutrient recycling. These conclusions add another dimension to bacterial mortality and the recycling of nutrients.

SUBMITTER: Williams HN

PROVIDER: S-EPMC4737939 | biostudies-literature | 2016 Feb

REPOSITORIES: biostudies-literature

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Halobacteriovorax, an underestimated predator on bacteria: potential impact relative to viruses on bacterial mortality.

Williams Henry N HN Lymperopoulou Despoina S DS Athar Rana R Chauhan Ashvini A Dickerson Tamar L TL Chen Huan H Laws Edward E Berhane Timkhite-Kulu TK Flowers Adrienne R AR Bradley Nadine N Young Shanterial S Blackwood Denene D Murray Jacqueline J Mustapha Oladipupo O Blackwell Cory C Tung Yahsuan Y Noble Rachel T RT

The ISME journal 20150807 2

Predation on bacteria and accompanying mortality are important mechanisms in controlling bacterial populations and recycling of nutrients through the microbial loop. The agents most investigated and seen as responsible for bacterial mortality are viruses and protists. However, a body of evidence suggests that predatory bacteria such as the Halobacteriovorax (formerly Bacteriovorax), a Bdellovibrio-like organism, contribute substantially to bacterial death. Until now, conclusive evidence has been ...[more]

PMID: 26251870

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Project description:Coral microbiomes are known to play important roles in organismal health, response to environmental stress, and resistance to disease. The coral microbiome contains diverse assemblages of resident bacteria, ranging from defensive and metabolic symbionts to opportunistic bacteria that may turn harmful in compromised hosts. However, little is known about how these bacterial interactions influence the mechanism and controls of overall structure, stability, and function of the microbiome. We sought to test how coral microbiome dynamics were affected by interactions between two bacteria: Vibrio coralliilyticus, a known temperature-dependent pathogen of some corals, and Halobacteriovorax, a unique bacterial predator of Vibrio and other gram-negative bacteria. We challenged reef-building coral with V. coralliilyticus in the presence or absence of Halobacteriovorax predators, and monitored microbial community dynamics with 16S rRNA gene profiling time-series. Vibrio coralliilyticus inoculation increased the mean relative abundance of Vibrios by greater than 35% from the 4 to 8 hour time point, but not in the 24 & 32 hour time points. However, strong secondary effects of the Vibrio challenge were also observed for the rest of the microbiome such as increased richness (observed species), and reduced stability (increased beta-diversity). Moreover, after the transient increase in Vibrios, two lineages of bacteria (Rhodobacterales and Cytophagales) increased in coral tissues, suggesting that V. coralliilyticus challenge opens niche space for these known opportunists. Rhodobacterales increased from 6.99% (±0.05 SEM) to a maximum mean relative abundance of 48.75% (±0.14 SEM) in the final time point and Cytophagales from <0.001% to 3.656%. Halobacteriovorax predators are commonly present at low-abundance on coral surfaces. Based on the keystone role of predators in many ecosystems, we hypothesized that Halobacteriovorax predators might help protect corals by consuming foreign or "alien" gram negative bacteria. Halobacteriovorax inoculation also altered the microbiome but to a lesser degree than V. coralliilyticus, and Halobacteriovorax were never detected after inoculation. Simultaneous challenge with both V. coralliilyticus and predatory Halobacteriovorax eliminated the increase in V. coralliilyticus, ameliorated changes to the rest of the coral microbiome, and prevented the secondary blooms of opportunistic Rhodobacterales and Cytophagales seen in the V. coralliilyticus challenge. These data suggest that, under certain circumstances, host-associated bacterial predators may mitigate the ability of other bacteria to destabilize the microbiome.

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Dataset Information

Halobacteriovorax, an underestimated predator on bacteria: potential impact relative to viruses on bacterial mortality.

Publications

Halobacteriovorax, an underestimated predator on bacteria: potential impact relative to viruses on bacterial mortality.

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