Search Results - (Author, Cooperation:E. G. Ruby)

2015-10-30

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Earth (Planet) ; Ecosystem ; Interdisciplinary Studies ; *Microbiota ; Oceans and Seas ; Seawater/microbiology ; *Soil Microbiology ; *Water Microbiology

1365-2958

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Medicine

mTn5Cm mutant of V. fischeri. In addition to the predicted defects in the efficiency of nitrogen utilization, this glnD mutant had an unexpected reduction in the ability to produce siderophore and grow under iron-limiting conditions. Although the glnD mutant could colonize juvenile squid normally over the first 24 h, it was subsequently unable to persist in the light organ to the usual extent. This persistence phenotype was more severe if the mutant was pregrown under iron-limiting conditions before inoculation, but could be ameliorated by the presence of excess iron. These results indicate that the ability to respond to iron limitation may be an important requirement in the developing symbiosis. Supplying the glnD gene in trans restored normal efficiency of nitrogen use, iron sequestration and colonization phenotypes to the glnD::mTn5Cm mutant; thus, there appears to be a genetic and/or metabolic linkage between nitrogen sensing, siderophore synthesis and symbiosis competence in V. fischeri that involves the glnD gene.

Electronic Resource

1432-1793

Springer Online Journal Archives 1860-2000

Biology

Abstract The intertidal polychaete Euzonus mucronata (Treadwell) is found in great numbers within beach sands that undergo periodic anoxia. Short-term exposures (2 to 4 h) to anaerobicity are withstood through the use of a supply of oxyhemoglobin to support continued aerobic metabolism. Longer periods of environmental anoxia activate an anaerobic metabolism capable of sustaining life for up to 20 days, and characterized by the excretion of succinate and propionate. These two mechanisms appear to be adaptations to the variations in occurrence and duration of anoxia within the intertidal sands inhabited by E. mucronata.

Electronic Resource

1432-1351

Biological rhythm ; Bioluminescence ; Symbiosis ; Vibrio fischeri ; Euprymna scolopes

Springer Online Journal Archives 1860-2000

Biology

Medicine

Abstract In most symbioses between animals and luminous bacteria it has been assumed that the bacterial symbionts luminesce continuously, and that the control of luminescent output by the animal is mediated through elaborate accessory structures, such as chromatophores and muscular shutters that surround the host light organ. However, we have found that while in the light organ of the sepiolid squid Euprymna scolopes, symbiotic cells of Vibrio fischeri do not produce a continuously uniform level of luminescence, but instead exhibit predictable cyclic fluctuations in the amount of light emitted per cell. This daily biological rhythm exhibits many features of a circadian pattern, and produces an elevated intensity of symbiont luminescence in juvenile animals during the hours preceding the onset of ambient darkness. Comparisons of the specific luminescence of bacteria in the intact light organ with that of newly released bacteria support the existence of a direct host regulation of the specific activity of symbiont luminescence that does not require the intervention of accessory tissues. A model encompassing the currently available evidence is proposed for the control of growth and luminescence activity in the E. scolopes/V. fischeri light organ symbiosis.

Electronic Resource

1432-072X

Vibrio fischeri ; Euprymna scolopes ; Symbiosis ; Growth ; Flagellation

Springer Online Journal Archives 1860-2000

Biology

Abstract A pure culture of the luminous bacterium Vibrio fischeri is maintained in the light-emitting organ of the sepiolid squid Euprymna scolopes. When the juvenile squid emerges from its egg it is symbiont-free and, because bioluminescence is part of an anti-predatory behavior, therefore must obtain a bacterial inoculum from the surrounding environment. We document here the kinetics of the process by which newly hatched juvenile squids become infected by symbiosis-competent V. fischeri. When placed in seawater containing as few as 240 colony-forming-units (CFU) per ml, the juvenile became detectably bioluminescent within a few hours. Colonization of the nascent light organ was initiated with as few as 1 to 10 bacteria, which rapidly began to grow at an exponential rate until they reached a population size of approximately 105 cells by 12 h after the initial infection. Subsequently, the number of bacteria in the established symbiosis was maintained essentially constant by a combination of both a 〉20-fold reduction in bacterial growth rate, and an expulsion of excess bacteria into the surrounding seawater. While V. fischeri cells are normally flagellated and motile, these bacteria did not elaborate these appendages once the symbiosis was established; however, they quickly began to synthesize flagella when they were removed from the light organ environment. Thus, two important biological characteristics, growth rate and flagellation, were modulated during establishment of the association, perhaps as part of a coordinated series of symbiotic responses.

Electronic Resource

1432-072X

Bdellovibrio bacteriovorus ; Unbalanced growth ; Growth kinetics ; Bacterial DNA replication

Springer Online Journal Archives 1860-2000

Biology

Abstract In this study we have investigated the rates and spatial patterns of chromosome replication and cell elongation during the growth phase of wild-type and facultatively prey-independent mutant strains of Bdellovibrio bacteriovorus. For the facultatively prey-independent mutants, the total DNA content of synchronously growing cultures was found to increase exponentially, as the multiple chromosomes within each filamentous cell replicated simultaneously. Cell mass, measured as total cellular protein, also increased exponentially during this period, apparently by means of multiple elongation sites along the filament wall. The relative rates of DNA and protein synthesis were unbalanced during growth, however, with the cellular concentration of DNA increasing slightly faster than that of protein. The original cellular DNA: protein ratio was restored in the progeny cells by continued protein synthesis during the septation period that follows the termination of DNA replication. Because of technical problems, these experiments could not be conducted on the wild-type cells, but similar results are assumed. This unusual pattern of unbalanced growth may represent an adaptation by bdellovibrios to maximize their progeny yield from the determinate amount of substrate available within a given prey cell.

Electronic Resource

1432-072X

Key wordsVibrio salmonicida ; Luminescence ; Luciferase ; Autoinducer ; Quorum sensing

Springer Online Journal Archives 1860-2000

Biology

Abstract The recent discovery that the fish pathogen Vibrio salmonicida is closely related to the luminous bacteria Vibrio fischeri and Vibrio logei suggested that V. salmonicida might also be capable of bioluminescence. Interestingly, cells of V. salmonicida were found to produce light in culture, but only when exposed to either an aliphatic aldehyde and/or the major V. fischeri autoinducer N-(3-oxo-hexanoyl)-l-homoserine lactone, a transcriptional activator of the luminescence (lux) genes. An extract of spent medium of V. salmonicida that should contain any V. salmonicida acyl-homoserine lactone autoinducer, when added to V. fischeri cells, led to an induction of their luminescence. These results show that V. salmonicida is a newly recognized luminous bacterial species that apparently both produces an autoinducer activity and responds to exogenous V. fischeri autoinducer.

Electronic Resource