Production of burukutu with Saccharomyces cerevisiae variants

Summary Physiological variants of Saccharomyces cerevisiae have been identified from burukutu and Raphia palm wine. Genomic DNA from the three S. cerevisiae variants had 38–40% G+C. Mixed fermentation of burukutu wort with each of the S. cerevisiae variants and bacterial species (Lactobacillus brevis, L. plantarum and Lactococcus lactis) produced burukutu of 3.1–4.0% alcoholic content.     

The microbiology of mutability

Bacteria possessing elevated spontaneous mutation rates are prevalent in certain environments, which is a paradox because most mutations are deleterious. For example, cells with defects in the methyl-directed mismatch repair (MMR) system, termed mutators or hypermutators, are overrepresented in populations of bacterial pathogens, with the mutator trait hypothesized to be advantageous in the changing host enviroments faced during colonization and establishment of chronic infections. Error-prone DNA polymerases, such as polIV and polV, function in translesion DNA synthesis, a DNA damage response that ensures genome integrity with a cost of increased mutation. While the biochemical aspects of these mutability pathways are well understood, the biological impacts have received less attention. Here, an examination of bacterial mutability systems and specifically the ecological and evolutionary context resulting in the selection of these systems is carried out.     

The microbiology of asthma

Asthma remains an important human disease that is responsible for substantial worldwide morbidity and mortality. The causes of asthma are multifactorial and include a complex mix of environmental, immunological and host genetic factors. In addition, epidemiological studies show strong associations between asthma and infection with respiratory pathogens, including common respiratory viruses such as rhinoviruses, human respiratory syncytial virus, adenoviruses, coronaviruses and influenza viruses, as well as bacteria (including atypical bacteria) and fungi. In this Review, we describe the many roles of microorganisms in the risk of developing asthma and in the pathogenesis of and protection against the disease, and we discuss the mechanisms by which infections affect the severity and prevalence of asthma.     

The role of lager beer yeast in oxidative stability of model beer

Aims: In this study, we investigated the relationship between the ability of lager brewing yeast strains to tolerate oxidative stress and their ability to produce oxidative stable model beer. Methods and Results: Screening of 21 lager brewing yeast strains against diamide and paraquat showed that the oxidative stress resistance was strain dependent. Fermentation of model wort in European Brewing Convention tubes using three yeast strains with varying oxidative stress resistances resulted in three model beers with different rates of radical formation as measured by electron spin resonance in forced ageing experiments. Interestingly, the strain with the lowest oxidative stress resistance and lowest secretion of thioredoxin, as measured by Western blotting, resulted in the highest uptake of iron, as measured by inductively coupled plasma‐mass spectrometry, and the slowest formation of radicals in the model beers. Conclusions: A more oxidative stable beer is not obtained by a more‐oxidative‐stress‐tolerant lager brewing yeast strain, exhibiting a higher secretion of thioredoxin, but rather by a less‐oxidative‐stress‐tolerant strain, exhibiting a higher iron uptake. Significance and Impact of the Study: To obtain lager beers with enhanced oxidative stability, yeast strains should be screened for their low oxidative stress tolerance and/or high ability to take up iron rather than for their high oxidative stress tolerance and/or high ability to secrete thioredoxin.     

The renaissance of microbiology.

Microbiology is finally occupying its true position as the pre-eminent field in life sciences. This is due to advances in molecular techniques that confirm the evolutionary significance of the biology of microbes. It is anticipated that the use of comparative genomics will provide information that will advance the understanding of mechanisms of pathogenesis and the importance of secondary metabolism in social microbiology. More emphasis on studies of microbial diversity will increase its value in both fundamental microbiology and its industrial applications.     

The microbiology of metalworking fluids

Metalworking fluids (MWFs) are complex mixtures of chemicals and are indispensable materials in industry. They are used as cooling and lubricating agents in different machining process such as grinding, milling, and cutting. The quality of MWFs is affected by physical, chemical, and microbial contaminates. In particular, MWFs are highly vulnerable to microbial contamination, which may act both as potential pathogens and deteriorgens. Microbial contamination is of major concern due to potential health hazards such as skin dermatitis and hypersensitivity pneumonitis. The contaminated MWFs can exhibit high degrees of microbial loading, ranging from 10(4) to 10(10) colony-forming units (CFU)/ml. Wide varieties of microorganisms are reported to colonize MWFs. Traditional culturing techniques are not only laborious and time consuming but also underestimate the actual distribution of the microorganisms present in the contaminated MWFs. Therefore, rapid molecular methods such as real-time PCR and fluorescent in situ hybridization are implemented to monitor the microbial load. In industry, biocides are presently used to control microbial contamination. However, it has its own disadvantages and therefore, in recent years, alternative methods such as UV irradiation were evaluated to reduce microbial contamination in MWFs. Microbes inhabiting the MWF are also capable of forming biofilm which is detrimental to the MWF system. Biofilm is resistant to common disinfectant methods, and thus further research and development is required to effectively control its formation within MWF systems. This review is intended to discuss the overall microbiological aspects of MWF.     

The microbiology of cut-away peat

Summary Fungi occurring commonly in cut-away peat were selected for autecological study, being chosen to represent both cosmopolitan and indigenous elements of the peat flora. A fungus alien to peat,Fusarium culmorum, was also included in the study. The germination in peat of the spores of these species and their ability to grow and colonise organic material added to peat were examined. It was concluded that the cosmopolitan element was composed of efficient saprophytes but that the ability of their spores to germinate in unamended peat was limited. Although Fusarium spores germinated, the germ tubes subsequently formed chlamydospores. Only spores of the indigenous peat fungi germinated well in peat but their growth habit was not suited to the colonisation and utilisation of organic matter, added to peat, in competition with the cosmopolitan flora. The concept of ‘source potential’ is introduced to explain the variance in fungal growth from different substrate bases.     

高温菌研究进展

高温菌是一类特殊的极端环境生物。本文简要从高温菌生态、耐热性、基因组等方面综述了高温菌的研究进展。