MicrobiologyBytes

Researchers examined the responses of various microorganisms (viruses, bacterial cells, bacterial and fungal spores, and lichens) to selected factors of space (microgravity, galactic cosmic radiation, solar UV radiation, and space vacuum) in space and laboratory simulation experiments. In general, microorganisms tend to thrive in the space flight environment in terms of enhanced growth parameters and a demonstrated ability to proliferate in the presence of normally inhibitory levels of antibiotics. The mechanisms responsible for the observed biological responses, however, are not yet fully understood. A hypothesized interaction of microgravity with radiation-induced DNA repair processes was experimentally refuted.

The survival of microorganisms in outer space was investigated to tackle questions on the upper boundary of the biosphere and on the likelihood of interplanetary transport of microorganisms. It was found that extraterrestrial solar UV radiation was the most deleterious factor of space. Among all organisms tested, only lichens (Rhizocarpon geographicum and Xanthoria elegans) maintained full viability after 2 weeks in outer space, whereas all other test systems were inactivated by orders of magnitude. Using optical filters and spores of Bacillus subtilis as a biological UV dosimeter, it was found that the current ozone layer reduces the biological effectiveness of solar UV by 3 orders of magnitude. If shielded against solar UV, spores of B. subtilis were capable of surviving in space for up to 6 years, especially if embedded in clay or meteorite powder (artificial meteorites). The data support the likelihood of interplanetary transfer of microorganisms within meteorites, the so-called lithopanspermia hypothesis.

Space microbiology. (2010) Microbiol Mol Biol Rev. 74(1): 121-56

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Bacillus thuringiensis (Bt) is an insecticidal bacterium that has successfully been used as a biopesticide for many years. It is usually referred to as a soil-dwelling organism, as a result of the prevalence of its spores in this environment, but one that can act as an opportunistic pathogen under appropriate conditions. Our understanding of the biology of this organism has been challenged further by the publication of two reports that claim that Bt requires the co-operation of commensal bacteria within the gut of a susceptible insect for its virulence. Perhaps Bt is not primarily a saprophyte and does not require the assistance of commensal bacteria but is a true pathogen in its own right and furthermore that its primary means of reproduction is in an insect?

Bacillus thuringiensis: an impotent pathogen? Trends Microbiol. 2010 18 (5): 189-194

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How do marine microbial ecosystems respond to climate change and pollution? In this article in Microbiology Today, Jack Gilbert explains how treating microbial marine communities as single cells in a metatranscriptomics approach could shed light on this fundamental question:

If the number of known stars in the Milky Way is multiplied by the number of known galaxies in the universe the result is a huge number, a septillion (1×10²⁴). Yet, large as this is, it pales in comparison to the number of microbial cells found in the world oceans, estimated to be 1 nonillion (1×10³⁰). When we start to include soil, air and organism-associated environments, this number becomes unimaginable. Traditional microbiology is our gold standard for understanding how these trillions and trillions of bacteria function. Basically, we grow the bugs in a laboratory, one species at a time, and test how they respond to chemical stimuli. Ultimately, we sequence their genome and try to map their genes to particular functions. To help make this link we can observe the expression of these genes in response to certain stimuli, so called transcriptomics.

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Cyanobacteria are the most environmentally significant group of bacteria on Earth. In this article in Microbiology Today, David Adams explains how in many ways life on Earth owes its very existence to this ancient group of micro-organisms:

Cyanobacteria are a huge group of photosynthetic bacteria found in almost every environment on Earth, including many of those most inhospitable to life, such as hot springs, deserts and the Antarctic. They are also enormously abundant, particularly in the oceans, and are primary producers, meaning that they fix CO₂ and in many cases also N₂; as a consequence they have an immense influence on the planet’s nutrient cycles and even its weather. Life on Earth owes a further great debt to this group of bacteria because their evolution of oxygenic photosynthesis, in which oxygen is released from the splitting of water, resulted in the eventual oxygenation of the atmosphere, providing the stimulus for the evolution of complex life forms. In addition, cyanobacteria are the ancestors of plastids, the photosynthetic organelles of today’s algae and plants.

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Eukaryotic marine parasites could have a wide impact on marine ecology. This article in Microbiology Today describes the role of these parasites in processes as diverse as species competition, carbon cycling and gene transfer:

Parasites are typically small organisms that exploit their host both as a food source and as a habitat. Although well-studied as human pathogens and organisms prejudicial to human interests, they have been persistently ignored in microbial aquatic ecology. Increased awareness of the important role of viruses in marine aquatic ecosystems in processes as diverse as species competition, carbon cycling, and gene transfers has recently changed our overall view of aquatic parasites. Recent evidence of the widespread occurrence of small eukaryotic parasites, requiring eukaryotic hosts, has highlighted the existence of another kind of pathogen which potentially has specific ecological roles.

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Indoor environments, where the average person in an industrial nation spends ~90% of his or her life, represent the most important interface between humans and microbes. Examples of well-known fungi include a few human pathogens, allergens, agents of structural rot and food spoilers. Indoor fungi’s prominent role in successful litigation around the world contributes to rising costs for various industries and insurance companies. Increasingly strict standards for indoor sanitation have resulted in regulatory agencies and private industries seeking to quantify building health. Mould surveys that target the relatively few visibly apparent fungal species or those readily cultivable on artificial media are now standard, and a U.S. Environmental Protection Agency-developed set of real-time PCR probes facilitates their quantification. However, the recent rise in fungal infections caused by species formerly considered benign but now seen as causing disease in immunosuppressed humans, and a vastly increased resolution of indoor fungal composition afforded by culture-independent sampling methods, force us to reconsider what constitutes a normal indoor environment and the factors that shape it. Recent efforts to describe the processes shaping indoor and urban fungal composition show temporal effects and modest correlations with human activity. The existence of global-scale patterns in fungal composition, however, is unexamined, despite evidence of biogeographical patterning in other microbial systems.

As with larger organisms, bacterial and archaeal composition is determined by both the contemporary environment and historical processes such as dispersal. The relative importance of these factors and the particular environmental variables involved depend on the taxa and habitat sampled. For indoor fungi whose association with highly mobile humans presents opportunities for global dispersal, it was presumed that most taxa would be relatively cosmopolitan on a global scale, and that the local indoor environment (as determined by building function, construction material, or circulation system) would play a relatively large role in shaping composition. As a result of the combination of presumably high dispersal rates between indoor habitats and the highly selective indoor environment, little influence of the outdoor environment was expected on fungal composition. But are these assumptions true?

Indoor fungal composition is geographically patterned and more diverse in temperate zones than in the tropics. PNAS USA June 28 2010 doi: 10.1073/pnas.100045410
Fungi are ubiquitous components of indoor human environments, where most contact between humans and microbes occurs. The majority of these organisms apparently play a neutral role, but some are detrimental to human lifestyles and health. Recent studies that used culture-independent sampling methods demonstrated a high diversity of indoor fungi distinct from that of outdoor environments. Others have shown temporal fluctuations of fungal assemblages in human environments and modest correlations with human activity, but global-scale patterns have not been examined, despite the manifest significance of biogeography in other microbial systems. Here we present a global survey of fungi from indoor environments using both taxonomic and phylogeny-informative molecular markers to determine whether global or local indoor factors determine indoor fungal composition. Contrary to common ecological patterns, we show that fungal diversity is significantly higher in temperate zones than in the tropics, with distance from the equator being the best predictor of phylogenetic community similarity. Fungal composition is significantly auto-correlated at the national and hemispheric spatial scales. Remarkably, building function has no significant effect on indoor fungal composition, despite stark contrasts between architecture and materials of some buildings in close proximity. Distribution of individual taxa is significantly range- and latitude-limited compared with a null model of randomized distribution. Our results suggest that factors driving fungal composition are primarily global rather than mediated by building design or function.

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The ocean is teaming with sunken treasure and for some treasure hunters the sand itself is the target. In this article in Microbiology Today, Jem Stach tells how novel actinomycetes on the seabed could be a source of much-needed novel antimicrobial drugs:

For most, the search for sunken treasure evokes images of glistening gold discovered when a diver’s hand wafts away the sand. However, for another kind of treasure hunter, the bioprospector, the sand itself is the target, brought from the depths of the sea, to the laboratory bench. In this case, the bioprospector is interested in marine microbes and their potential to produce antimicrobial compounds. With global sales of these life-saving products set to exceed $100 billion by 2015, such micro-organisms could be worth more than their weight in gold.

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Amazingly, all the phages on Earth, if placed end to end, would probably extend a distance equivalent to that of the nearest 60 galaxies. In this article in Microbiology Today, Eric Wommack explains how metagenomics is gradually revealing the amazing diversity and abundance of viruses in the biosphere:

Although the throughput and accuracy of methods for viral direct counting has improved since the 1989 report based on transmission electron microscopy, the ‘factor of 10’ ratio of virus to bacterial abundance within aquatic environments has remained a surprisingly common observation. Extrapolating the ‘factor of 10’ rule to the biosphere has lead to estimates that global viral abundance is in the order of 10³¹ individuals. Assuming an average length dimension of 100 nm, Curtis Suttle has proposed that, lined end-to-end, all the phages on earth would extend a distance equivalent to that of the nearest 60 galaxies (10 million light years, 10²⁴m).

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Air conditioning systems are present in many modern cars. The advantages of air conditioning such as comfort in the summer time are well-known. However, the potential risk of contamination of the air in the cabin by microorganisms by the air conditioning system has yet rarely been examined. A new study looked at influence of AC systems in cars on the quality of filtered air from the outside and air re-circulating from the car’s cabin under various conditions. The result?

The microbiological quality of air improves when using air conditioning systems in cars. BMC Infectious Diseases 2010, 10: 146 doi:10.1186/1471-2334-10-146
Air conditioning systems are a common feature in automobiles these days. However, its impact on the number of particles and microorganisms inside the vehicle – and by this its impact on the risk of an allergic reaction – is yet unknown. Over a time period of 30 months, the quality of air was investigated in three different types of car that were all equipped with a automatic air conditioning system. Operation modes using fresh air from outside the car as well as circulating air from inside the car were examined. The total number of microorganisms and the number of mold spores were measured by impaction in a high flow air sampler. Particles of 0.5 to 5.0 µm diameter were counted by a laser particle counter device. Overall 32 occasions of sampling were performed. The concentration of microorganisms outside the cars was always higher than it was inside the cars. Few minutes after starting the air conditioning system the total number of microorganisms was reduced by 81%, the number of mold spores was reduced by 83.3%, and the number of particles was reduced by 87%. There were no significant differences neither between the types of cars nor between the types of operation mode of the air conditioning system (fresh air vs. circulating air). All parameters that were looked for in this study improved during utilization of the car’s air conditioning system. We believe that the risk of an allergic reaction will be reduced during use also. Nevertheless, we recommend regular maintenance of the system and replacement of older filters after defined changing intervals.

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