Leaky resistance and the conditions for the existence of lytic bacteriophage

PLOS Biology (new articles) - 5 hours 27 min назад

by Waqas N. Chaudhry, Maroš Pleška, Nilang N. Shah, Howard Weiss, Ingrid C. McCall, Justin R. Meyer, Animesh Gupta, Călin C. Guet, Bruce R. Levin

In experimental cultures, when bacteria are mixed with lytic (virulent) bacteriophage, bacterial cells resistant to the phage commonly emerge and become the dominant population of bacteria. Following the ascent of resistant mutants, the densities of bacteria in these simple communities become limited by resources rather than the phage. Despite the evolution of resistant hosts, upon which the phage cannot replicate, the lytic phage population is most commonly maintained in an apparently stable state with the resistant bacteria. Several mechanisms have been put forward to account for this result. Here we report the results of population dynamic/evolution experiments with a virulent mutant of phage Lambda, λVIR, and Escherichia coli in serial transfer cultures. We show that, following the ascent of λVIR-resistant bacteria, λVIR is maintained in the majority of cases in maltose-limited minimal media and in all cases in nutrient-rich broth. Using mathematical models and experiments, we show that the dominant mechanism responsible for maintenance of λVIR in these resource-limited populations dominated by resistant E. coli is a high rate of either phenotypic or genetic transition from resistance to susceptibility—a hitherto undemonstrated mechanism we term "leaky resistance." We discuss the implications of leaky resistance to our understanding of the conditions for the maintenance of phage in populations of bacteria—their “existence conditions.”
Категории: Biology, Journals

Corals on old North Sea oil rigs could help natural reefs recover

Genetics - чт, 2018-08-16 16:00
Not only are deep-sea coral ecosystems thriving on oil and gas rigs in the North Sea, their larvae may be helping repopulate damaged natural reefs
Категории: Biology

Replacing your boss with a cruel robot could make you concentrate more

Genetics - чт, 2018-08-16 14:43
A mean robot watching over you increases your focus on the most important parts of a task more than a friendly robot or even no robot at all
Категории: Biology

Meet the ‘climate kids’ suing the US government over global warming

Genetics - чт, 2018-08-16 14:00
They claim inaction on climate change has blighted their future – just one of many challenges now hitting the courts. And they might just succeed
Категории: Biology

Why the US is worried a Russian satellite might be a space weapon

Genetics - чт, 2018-08-16 13:55
A Russian satellite has been getting closer to Earth without a clear reason and US officials are concerned that it could be a space weapon
Категории: Biology

A drug’s weird side effect lets people control their dreams

Genetics - чт, 2018-08-16 13:54
Researchers have developed the most effective technique for lucid dreaming yet, and it may allow people to fulfil fantasies and overcome nightmares and phobias
Категории: Biology

An opt-out organ donor system might actually lead to fewer transplants

Genetics - чт, 2018-08-16 07:01
England’s plans to make everyone an organ donor by default could make families less likely to give consent, perhaps leading to a fall in transplant operations
Категории: Biology

Exposure to insecticide DDT linked to having a child with autism

Genetics - чт, 2018-08-16 07:00
Although DDT has been banned for decades in many countries, exposure to its breakdown products may be influencing whether mothers have autistic babies
Категории: Biology

Call combinations in birds and the evolution of compositional syntax

PLOS Biology (new articles) - ср, 2018-08-15 23:00

by Toshitaka N. Suzuki, David Wheatcroft, Michael Griesser

Syntax is the set of rules for combining words into phrases, providing the basis for the generative power of linguistic expressions. In human language, the principle of compositionality governs how words are combined into a larger unit, the meaning of which depends on both the meanings of the words and the way in which they are combined. This linguistic capability, i.e., compositional syntax, has long been considered a trait unique to human language. Here, we review recent studies on call combinations in a passerine bird, the Japanese tit (Parus minor), that provide the first firm evidence for compositional syntax in a nonhuman animal. While it has been suggested that the findings of these studies fail to provide evidence for compositionality in Japanese tits, this criticism is based on misunderstanding of experimental design, misrepresentation of the importance of word order in human syntax, and necessitating linguistic capabilities beyond those given by the standard definition of compositionality. We argue that research on avian call combinations has provided the first steps in elucidating how compositional expressions could have emerged in animal communication systems.
Категории: Biology, Journals

Compositionality in animals and humans

PLOS Biology (new articles) - ср, 2018-08-15 23:00

by Simon W. Townsend, Sabrina Engesser, Sabine Stoll, Klaus Zuberbühler, Balthasar Bickel

A key step in understanding the evolution of human language involves unravelling the origins of language’s syntactic structure. One approach seeks to reduce the core of syntax in humans to a single principle of recursive combination, merge, for which there is no evidence in other species. We argue for an alternative approach. We review evidence that beneath the staggering complexity of human syntax, there is an extensive layer of nonproductive, nonhierarchical syntax that can be fruitfully compared to animal call combinations. This is the essential groundwork that must be explored and integrated before we can elucidate, with sufficient precision, what exactly made it possible for human language to explode its syntactic capacity, transitioning from simple nonproductive combinations to the unrivalled complexity that we now have.
Категории: Biology, Journals

Serial representation of items during working memory maintenance at letter-selective cortical sites

PLOS Biology (new articles) - ср, 2018-08-15 23:00

by Ali Bahramisharif, Ole Jensen, Joshua Jacobs, John Lisman

A key component of working memory is the ability to remember multiple items simultaneously. To understand how the human brain maintains multiple items in memory, we examined direct brain recordings of neural oscillations from neurosurgical patients as they performed a working memory task. We analyzed the data to identify the neural representations of individual memory items by identifying recording sites with broadband gamma activity that varied according to the identity of the letter a subject viewed. Next, we tested a previously proposed model of working memory, which had hypothesized that the neural representations of individual memory items sequentially occurred at different phases of the theta/alpha cycle. Consistent with this model, the phase of the theta/alpha oscillation when stimulus-related gamma activity occurred during maintenance reflected the order of list presentation. These results suggest that working memory is organized by a cortical phase code coordinated by coupled theta/alpha and gamma oscillations and, more broadly, provide support for the serial representation of items in working memory.
Категории: Biology, Journals

No contraceptive is perfect, but can you trust apps to stop pregnancy?

Genetics - ср, 2018-08-15 20:00
Birth control app Natural Cycles has come under fire for unwanted pregnancies, but this just reveals how little we understand contraception
Категории: Biology

Extreme tales from a record-breaking dive in the Antarctic

Genetics - ср, 2018-08-15 19:30
Jon Copley dived deep for Blue Planet II. He reveals the risks of falling rocks, leaks and fires inside the sub, and highlights the extraordinary "death star"
Категории: Biology

Some clouds are formed when a virus makes algae shed their shells

Genetics - ср, 2018-08-15 18:00
When algae in the ocean get a virus, they shed their exoskeleton and those chalky bits can get flung into the air and trigger the formation of clouds
Категории: Biology

Doctors will grow human tissue on the International Space Station

Genetics - ср, 2018-08-15 16:54
Liver tissue and muscle fibre are going to be grown on the ISS, to see if we can one day grow human organs in space
Категории: Biology

This one particle could solve five mega-mysteries of physics

Genetics - ср, 2018-08-15 14:00
Forget the Higgs: theorists have uncovered a missing link that explains dark matter, what happened in the big bang and more. Now they’re racing to find it
Категории: Biology

Weird circles in the sky may be signs of a universe before ours

Genetics - ср, 2018-08-15 10:00
A theory suggesting that the universe is constantly reborn could be proved right by ‘Hawking points’ – signs of evaporated black holes from a time before the big bang
Категории: Biology

Why taking ayahuasca is like having a near-death experience

Genetics - ср, 2018-08-15 06:00
A psychedelic drug produces effects similar to near-death experiences. The finding suggests changes to brain activity may explain such paranormal phenomena
Категории: Biology

Sterile fish could help wild salmon dodge the ‘gene pollution’ effect

Genetics - ср, 2018-08-15 02:01
Farmed Atlantic salmon make the local wild salmon population weaker. Making them sterile could work – but there’s a catch
Категории: Biology

Sticking brain cells together with glue could boost and protect memory

Genetics - вт, 2018-08-14 19:43
Can a chemical that reinforces the connections in our brains prevent the destruction of memories in ageing and Alzheimer’s? It seems to work in mice
Категории: Biology