Raman spectroscopy reveals alteration of spore compositions under different nutritional conditions in Lysinibacillus boronitolerans YS11.

Little is known about final spores components when bacteria undergo sporulation under different nutrient conditions. Different degrees of resistance and germination rates were observed in the three types of spores of Lysinibacillus boronitolerans YS11 (SD, Spores formed in Difco sporulation medium™; SC and SF, Spores formed in an agricultural byproduct medium with 10 mM CaCl2 and with 10 mM FeSO4, respectively). Stronger UV resistance was recorded for SF with 1.8-2.3-fold greater survival than SC and SD under UV treatment. The three spore types showed similar heat resistances at 80°C, but survival rates of SC and SD were much higher (∼1,000 times) than those of SF at 90°C. However, germination capacity of SF was 20% higher than those of SD and SC on Luria-Bertani agar plates for 24 h. SF germinated more rapidly in a liquid medium with high NaCl concentrations than SC and SD, but became slower under alkaline conditions. Raman spectroscopy was used to analyze the heterogeneities in the three types of vegetative cells and their spores under different nutritional conditions. Exponentially grown-each vegetative cells had different overall Raman peak values. Raman peaks of SC, SD, and SF also showed differences in adenine and amide III compositions and nucleic acid contents. Our data along with Raman spectroscopy provided the evidence that spores formed under under different growth conditions possess very different cellular components, which affected their survival and germination rates.

Resistance and Raman spectroscopy analysis of Parageobacillus thermantarcticus spores after γ-ray exposure.

Spores of the genus Bacillus are able to resist ionizing radiations and therefore they are a suitable biological model for studies in Astrobiology, i.e. the multidisciplinary approach to the study of the origin and evolution of life on Earth and in the universe. The resistance to γ-radiation is an important issue in Astrobiology in relation to the search for bacterial species that could adapt to life in space. This study investigates the resistance of spores of the thermophilic bacteria Parageobacillus thermantarcticus to γ-rays. The analysis of spores' response to irradiation at a molecular level is performed by means of Raman spectroscopy that allows to get insights in the sequence of events taking place during inactivation. The role of the γ-rays' dose in the inactivation of spores is also investigated, allowing to highlight the mechanism(s) of inactivation including DNA damage, protein denaturation and calcium dipicolinate levels.

Thermophilic bacteria in Moroccan hot springs, salt marshes and desert soils.

The diversity of thermophilic bacteria was investigated in four hot springs, three salt marshes and 12 desert sites in Morocco. Two hundred and forty (240) thermophilic bacteria were recovered, identified and characterized. All isolates were Gram positive, rod-shaped, spore forming and halotolerant. Based on BOXA1R-PCR and 16S rRNA gene sequencing, the recovered isolates were dominated by the genus Bacillus (97.5%) represented by B. licheniformis (119), B. aerius (44), B. sonorensis (33), B. subtilis (subsp. spizizenii (2) and subsp. inaquosurum (6)), B. amyloliquefaciens (subsp. amyloliquefaciens (4) and subsp. plantarum (4)), B. tequilensis (3), B. pumilus (3) and Bacillus sp. (19). Only six isolates (2.5%) belonged to the genus Aeribacillus represented by A. pallidus (4) and Aeribacillus sp. (2). In this study, B. aerius and B. tequilensis are described for the first time as thermophilic bacteria. Moreover, 71.25%, 50.41% and 5.41% of total strains exhibited high amylolytic, proteolytic or cellulolytic activity respectively.

Thermophilic bacteria in Moroccan hot springs, salt marshes and desert soils

The diversity of thermophilic bacteria was investigated in four hot springs, three salt marshes and 12 desert sites in Morocco. Two hundred and forty (240) thermophilic bacteria were recovered, identified and characterized. All isolates were Gram positive, rod-shaped, spore forming and halotolerant. Based on BOXA1R-PCR and 16S rRNA gene sequencing, the recovered isolates were dominated by the genus Bacillus (97.5%) represented by B. licheniformis (119), B. aerius (44), B. sonorensis (33), B. subtilis (subsp. spizizenii (2) and subsp. inaquosurum (6)), B. amyloliquefaciens (subsp. amyloliquefaciens (4) and subsp. plantarum (4)), B. tequilensis (3), B. pumilus (3) and Bacillus sp. (19). Only six isolates (2.5%) belonged to the genus Aeribacillus represented by A. pallidus (4) and Aeribacillus sp. (2). In this study, B. aerius and B. tequilensis are described for the first time as thermophilic bacteria. Moreover, 71.25%, 50.41% and 5.41% of total strains exhibited high amylolytic, proteolytic or cellulolytic activity respectively.

Characterization of potential stress responses in ancient Siberian permafrost psychroactive bacteria.

Past studies of cold-acclimated bacteria have focused primarily on organisms not capable of sub-zero growth. Siberian permafrost isolates Exiguobacterium sp. 255-15 and Psychrobacter sp. 273-4, which grow at subzero temperatures, were used to study cold-acclimated physiology. Changes in membrane composition and exopolysaccharides were defined as a function of growth at 24, 4 and -2.5 degrees C in the presence and absence of 5% NaCl. As expected, there was a decrease in fatty acid saturation and chain length at the colder temperatures and a further decrease in the degree of saturation at higher osmolarity. A shift in carbon source utilization and antibiotic resistance occurred at 4 versus 24 degrees C growth, perhaps due to changes in the membrane transport. Some carbon substrates were used uniquely at 4 degrees C and, in general, increased antibiotic sensitivity was observed at 4 degrees C. All the permafrost strains tested were resistant to long-term freezing (1 year) and were not particularly unique in their UVC tolerance. Most of the tested isolates had moderate ice nucleation activity, and particularly interesting was the fact that the Gram-positive Exiguobacterium showed some soluble ice nucleation activity. In general the features measured suggest that the Siberian organisms have adapted to the conditions of long-term freezing at least for the temperatures of the Kolyma region which are -10 to -12 degrees C where intracellular water is likely not frozen.

Resistance of vegetative cells and endospores of Sporolactobacillus to gamma-irradiation.

Vegetative cells of Sporolactobacillus showed average resistance to gamma-irradiation compared to other vegetative bacteria with D10 values ranging from 0.350 to 0.525 kGy. Endospores of Sporolactobacillus showed higher resistance to gamma-irradiation than most Bacillus species but were close to that of Clostridium species. The average D10 value for Sporolactobacillus endospores was 2.5 kGy.