MICROBIA. Oldest of Earth's communities gets scrutiny. 2005 - 2020

Links to Pub-Med abstracts on scientific journal articles relating to microbiology and microsociology, quorum sensing and biofilm formation & excerpts from the abstracts.

2020

2020 Quorum sensing regulates 'swim-or-stick' lifestyle in the phycosphere " Interactions between phytoplankton and bacteria play major roles in global biogeochemical cycles and oceanic nutrient fluxes. These interactions occur in the microenvironment surrounding phytoplankton cells, known as the phycosphere. 

Bacteria in the phycosphere use either chemotaxis or attachment to benefit from algal excretions. Both processes are regulated by quorum sensing (QS), a cell-cell signalling mechanism that uses small infochemicals to coordinate bacterial gene expression"

2020 Inhibiting bacterial cooperation is an evolutionarily robust anti-biofilm strategy  " Bacteria commonly form dense biofilms encased in extracellular polymeric substances (EPS). Biofilms are often extremely tolerant to antimicrobials but their reliance on shared EPS may also be a weakness as social evolution theory predicts that inhibiting shared traits can select against resistance. 

Here we show that extracellular polymeric substances extruded as...biofilms is a cooperative trait whose benefit is shared among cells, and that EPS inhibition reduces both cell attachment and antimicrobial tolerance. 

We then compare an EPS inhibitor to conventional antimicrobials in an evolutionary experiment. While resistance against conventional antimicrobials rapidly evolves, we see no evolution of resistance to EPS inhibition. 

We further show that a resistant strain is outcompeted by a susceptible strain under EPS inhibitor treatment, explaining why resistance does not evolve. Our work suggests that targeting cooperative traits is a viable solution to the problem of antimicrobial resistance."

2019

2019  Surviving as a Community: Antibiotic Tolerance and Persistence in Bacterial Biofilms  "we review recent progress aimed at understanding the mechanical features that drive biofilm resilience and the biofilm formation process at single-cell resolution. We discuss findings regarding mechanisms underlying bacterial tolerance and persistence in biofilms and how these phenotypes are linked to antibiotic resistance. New strategies for combatting tolerance and persistence in biofilms and possible methods for biofilm eradication are highlighted to inspire future development."

2019  Quorum sensing in Vibrio spp.: the complexity of multiple signalling molecules in marine and aquatic environments  "Quorum sensing (QS) is a density-dependent mechanism enabling bacteria to coordinate their actions via the release of small diffusible molecules named autoinducers (AIs).  Vibrio spp. are able to adapt to changing environmental conditions by using a wide range of physiological mechanisms ...... Cell-to-cell communication controls many of their vital functions such as niche colonization, survival strategies. "

2019 Big Impact of the Tiny: Bacteriophage-Bacteria Interactions in Biofilms  "Bacteriophages (phage viruses) have been shaping bacterial ecology and evolution for millions of years, for example, by selecting for defence strategies. Evidence supports that bacterial biofilm formation is one such strategy and that biofilm-mediated protection against phage infection depends on maturation and composition of the extracellular matrix. Interestingly, studies have revealed that phages can induce and strengthen biofilms."

2019  Behavioral heterogeneity in quorum sensing can stabilize social cooperation in microbial populations  " Microbial communities are susceptible to the public goods dilemma, whereby individuals can gain an advantage within a group by utilizing, but not sharing the cost of producing, public goods. 

In bacteria, the development of quorum sensing (QS) can establish a cooperation system in a population by coordinating the production of costly and sharable extracellular products (public goods). Cooperators ..... are vulnerable to being undermined by QS-deficient defectors that escape from QS but benefit from the cooperation of others. 

Although microorganisms have evolved several mechanisms to resist cheating invasion in the public goods game, it is not clear why cooperators frequently coexist with defectors and how they form a relatively stable equilibrium during evolution."

"QS-directed social cooperation can select a conditional defection strategy prior to the emergence of QS-mutant defectors, depending on resource availability. Conditional defectors represent a QS-inactive state of wild type (cooperator) individual and can invade QS-activated cooperators by adopting a cheating strategy, and then revert to cooperating when there are abundant nutrient supplies irrespective of the exploitation of QS-mutant defector."

 "[T]he incorporation of conditional defection strategy into the framework of iterated public goods game with sound punishment mechanism can lead to the coexistence of cooperator, conditional defector, and defector in a rock-paper-scissors dynamics."

2018

2018  Maximizing Growth Yield and Dispersal via Quorum Sensing Promotes Cooperation in Vibrio Bacteria  "Quorum sensing (QS) is a form of bacterial chemical communication that regulates cellular phenotypes, including certain cooperative behaviors, in response to environmental and demographic changes. Despite the existence of proposed mechanisms that stabilize QS against defector exploitation, it is unclear if or how QS cooperators can proliferate in some model systems in populations mostly consisting of defectors. 

We predicted that growth in fragmented subpopulations could allow QS cooperators to invade a QS defector population. This could occur despite cooperators having lower relative fitnesses than defectors due to favored weighting of genotypes that produce larger populations of bacteria"

2018  Coumarin: a novel player in microbial quorum sensing and biofilm formation inhibition ". An intricate cell-cell communication system termed quorum sensing (QS) and the coordinated multicellular behaviour of biofilm formation have both been identified"...."QS systems allow bacteria to adapt rapidly to harsh conditions, and are known to promote the formation of antibiotic tolerant biofilm communities. It is well known that biofilm is a recalcitrant mode of growth and it also increases bacterial resistance to conventional antibiotics..... Reports have highlighted the potential role of coumarins as alternative therapeutic strategies based on their ability to block the QS signalling systems and to inhibit the formation of biofilms in clinically relevant pathogens."

2018 Archaeal biofilm formation  "Biofilms are structured and organized communities of microorganisms that represent one of the most successful forms of life on Earth. Bacterial biofilms have been studied in great detail, and many molecular details are known about the processes that govern bacterial biofilm formation, however, archaea are ubiquitous in almost all habitats on Earth and can also form biofilms. In recent years, insights have been gained into the development of archaeal biofilms, how archaea communicate to form biofilms and how the switch from a free-living lifestyle to a sessile lifestyle is regulated."

2017

2017 An Update on the Sociomicrobiology of Quorum Sensing in Gram-Negative Biofilm Development   "Bacteria are social creatures that are able to interact and coordinate behaviors with each other in a multitude of ways. The study of such group behaviors in microbes was coined “sociomicrobiology” in 2005. Two such group behaviors in bacteria are quorum sensing (QS) and biofilm formation. At a very basic level, QS is the ability to sense bacterial density via cell-to-cell signaling using self-produced signals called autoinducers, and biofilms are aggregates of cells that are attached to one another via a self-produced, extracellular matrix. 

"Formation of mature biofilms. In addition to attachment, QS regulates other aspects of biofilm formation, including accumulation of biofilm biomass, biofilm structure, and the dispersal of biofilm cells." "Since cells in biofilm aggregates are in close proximity, biofilms represent an ecologically relevant environment for QS."

2016

2016 Editorial: Signals to sociality: how microbial communication fashions communities  "[M]ost bacteria exist in nature in multifaceted communities that are often associated with living and non-living surfaces. Within these communities, bacteria are exchanging information with other bacteria and other organisms, including eukaryotes, to generate coordinated behaviors. 

Central to this microbial information exchange is communication between cells. The act of communication exists in many forms and is often considered essential for organized group behaviors between individuals and for the development of multicellular organisms.

2016 Editorial: Signals to sociality: how microbial communic fashions communities " "[M]ost bacteria exist in nature in multifaceted communities that are often associated with living and non-living surfaces. Within these communities, bacteria are exchanging information with other bacteria and other organisms, including eukaryotes, to generate coordinated behaviors. "

2016 Quorum sensing is a language of chemical signals and plays an ecological role  in algal-bacterial interactions   "Algae are ubiquitous in the marine environment, and the ways in which they interact with bacteria are of particular interest in marine ecology field. The interactions between primary producers and bacteria impact the physiology of both partners, alter the chemistry of their environment, and shape microbial diversity."

2016 Quorum Sensing and Quorum Quenching in the Phycosphere of Phytoplankton: a Case of Chemical Interactions in Ecology  "The interactions between bacteria and phytoplankton regulate many important biogeochemical reactions in the marine environment, including those in the global carbon, nitrogen, and sulfur cycles. At the microscopic level, it is now well established that important consortia of bacteria colonize the phycosphere, the immediate environment of phytoplankton cells. In this microscale environment, abundant bacterial cells are organized in a structured biofilm."

2015

2015 Quorum Sensing in Marine Microbial Environments  "Quorum sensing (QS) was first observed in a marine bacterium nearly four decades ago...Only in the past decade has there been a rise in interest in the role that QS plays in the ocean. 

"It has become clear that QS.... is involved in important processes within the marine carbon cycle, in the health of coral reef ecosystems, and in trophic interactions between a range of eukaryotes and their bacterial associates. "

"The most well-studied QS systems in the ocean occur in surface-attached (biofilm) communities...."   "QS is highly sensitive to the chemical and biological makeup of the environment and may respond to anthropogenic change, including ocean acidification and rising sea surface temperatures."

2012

2012 Interactions in Bacterial Biofilm Development: A Structural Perspective  "A community-based life style is the normal mode of growth and survival for many bacterial species. These cellular accretions or biofilms are initiated upon recognition of solid phases by cell surface exposed adhesive moieties. 

Further cell-cell interactions, cell signalling and bacterial replication leads to the establishment of dense populations encapsulated in a mainly self-produced extracellular matrix; this comprises a complex mixture of macromolecules. These fascinating architectures protect the inhabitants from radiation damage, dehydration, pH fluctuations and antimicrobial compounds"

2011

2011 "From Koch's Postulates to Socio-microbiology"  "The ability of bacteria to intercommunicate and process information about resource availability and the health status of the host has led to the concept of bacteria behaving like a social group. The study of social networks developed among bacteria in their natural habitats is called sociomicrobiology. From "Koch's Postulates to Socio-microbiology."

2011 The New Science of Sociomicrobiology and the realm of synthetic materials and systems ecology  "We need to remain cognizant that bacterial cells are individual organisms involved in complex social interactions. So not only do we need to think about systems and synthetic biology from a cellular perspective, but we need to think about systems and synthetic ecology too."

2011 Territoriality in Proteus: advertisement and aggression "Members of the bacterial species Proteus mirabilis are capable of rapid swarming over a hard agar surface. Swarming colonies display a striking phenotype in which a visible boundary forms between swarms of different strains. In contrast, boundaries do not arise between two swarms of a single strain (Figure 1). This behavior is a demonstration that P. mirabilis swarms are capable of territoriality and self versus non-self recognition"

"At the cellular level self vs non-self recognition is a behavior conserved throughout biology, from bacteria to animals and to vertebrate immune systems. The puzzle of how cells or organisms recognize and differentiate self from non-self is fundamental to fields as far from each other as immunology and ecology. 

The boundary formation between P. mirabilis is clearly a complex interplay of cell-to-cell communication and population development. In boundary formation, there is not only social recognition but also territorial competition between approaching Proteus strains. It seems likely that recognition and antagonism both play a role in the overall boundary formation process, but antagonism is not required for boundary formation. Molecular details of the dance leading to boundary formation remain to be determined.

2008

2008 Sociomicrobiology: The evolution of quorum sensing in bacterial biofilms  "Biofilms are surface-bound aggregates of bacteria that are held together by a matrix of extracellular polysaccharides (EPSs). Quorum sensing often controls the synthesis and secretion of EPSs, but although some bacteria switch on EPS production at high cell densities in biofilms, other bacteria switch it off. Nadell et al. used a model that simulates the growth of a simple biofilm to simulate competition between strains that had different EPSs and quorum-sensing phenotypes. This revealed that switching quorum sensing and EPSs off allows bacteria such as Pseudomonas aeruginosa to compete better in environments in which competition is prolonged and intense..."

2005

2005 Sociomicrobiology: the connections between quorum sensing and biofilms. Trends Microbiol 13: 27-33  [B]iofilms and quorum sensing represent two areas in which microbiologists focus on social aspects of bacteria. .....We believe that these two aspects of bacterial behavior represent a small part of the social repertoire of bacteria. Bacteria exhibit many social activities and they represent a model for dissecting social behavior at the genetic level. Therefore, we introduce the term 'sociomicrobiology'. "

"A clear challenge facing the field is to determine what parameters of a biofilm community influence the onset of quorum sensing and subsequent patterns of gene expression. Another key challenge is to determine the functional consequences of quorum sensing in a biofilm community...... Finally, the role of quorum sensing in mixed species systems remains to be explored. Does interspecies signaling occur frequently in mixed species systems, or do signal consuming organisms severely limit the extent of signaling that occurs? The answer to these questions will undoubtedly provide some expected results as well as surprises."

Investigations of the role quorum sensing plays in biofilm

systems for different organisms and how quorum sensing

works mechanistically in a biofilm community remain in

their infancy. A clear challenge facing the field is to

determine what parameters of a biofilm community

influence the onset of quorum sensing and subsequent

patterns of gene expression. Another key challenge is to

determine the functional consequences of quorum sensing

in a biofilm community. Does induction of quorum sensing

influence the pathogenic potential of biofilm communities

of some species, or perhaps alter the antimicrobial

tolerance of the biofilm? Finally, the role of quorum

sensing in mixed species systems remains to be explored.

Does interspecies signaling occur frequently in mixed

species systems, or do signal consuming organisms

severely limit the extent of signaling that occurs? The

answer to these questions will undoubtedly provide some

expected results as well as surprise

2002

Small Talk: Cell to cell Communication in Bacteria  Bonnie Bassler  "In a process called quorum sensing, groups of bacteria communicate with one another to coordinate their behavior and function like a multicellular organism. "

"Quorum sensing-controlled behaviors are those that only occur when bacteria are at high cell population densities. These behaviors are ones that are unproductive when undertaken by an individual bacterium but become effective by the simultaneous action of a group of cells. For example, quorum sensing regulates bioluminescence, virulence factor expression, biofilm formation, sporulation, and mating. "

"Quorum sensing is achieved through the production, release, and subsequent detection of and response to threshold concentrations of signal molecules called autoinducers. The accumulation of a stimulatory concentration of an extracellular autoinducer can only occur when a sufficient number of cells, a “quorum,” is present. "