Freezing and thawing in Antarctica: characterization of antifreeze protein (AFP) producing microorganisms isolated from King George Island, Antarctica.

Antarctic temperature variations and long periods of freezing shaped the evolution of microorganisms with unique survival mechanisms. These resilient organisms exhibit several adaptations for life in extreme cold. In such ecosystems, microorganisms endure the absence of liquid water and exhibit resistance to freezing by producing water-binding molecules such as antifreeze proteins (AFP). AFPs modify the ice structure, lower the freezing point, and inhibit recrystallization. The objective of this study was to select and identify microorganisms isolated from different Antarctic ecosystems based on their resistance to temperatures below 0 °C. Furthermore, the study sought to characterize these microorganisms regarding their potential antifreeze adaptive mechanisms. Samples of soil, moss, permafrost, and marine sediment were collected on King George Island, located in the South Shetland archipelago, Antarctica. Bacteria and yeasts were isolated and subjected to freezing-resistance and ice recrystallization inhibition (IR) tests. A total of 215 microorganisms were isolated, out of which 118 were molecularly identified through molecular analysis using the 16S rRNA and ITS regions. Furthermore, our study identified 24 freezing-resistant isolates, including two yeasts and 22 bacteria. A total of 131 protein extracts were subjected to the IR test, revealing 14 isolates positive for AFP production. Finally, four isolates showed both freeze-resistance and IR activity (Arthrobacter sp. BGS04, Pseudomonas sp. BGS05, Cryobacterium sp. P64, and Acinetobacter sp. M1_25C). This study emphasizes the diversity of Antarctic microorganisms with the ability to tolerate freezing conditions. These microorganisms warrant further investigation to conduct a comprehensive analysis of their antifreeze capabilities, with the goal of exploring their potential for future biotechnological applications.

Sourdough bacterial dynamics revealed by metagenomic analysis in Brazil.

This study dealt with the influence of the temperature on the bacterial dynamics of two spontaneously fermented wheat sourdoughs, propagated at 21 ±â€¯1 °C (SD1) and 30 ±â€¯1 °C (SD2), during nine backslopping steps (BS1 to BS9). Proteobacteria was the only phylum found in flour. Escherichia hermannii was predominant, followed by Kosakonia cowanii, besides species belonging to the genera Pantoea and Pseudomonas. After one step of propagation, Clostridium and Bacillus cereus group became predominant. Lactobacillus curvatus was found at low relative abundance. For the second backslopping step, Clostridium was flanked by L. curvatus and Lactobacillus farciminis. From BS4 (6th day) onward, lactic acid bacteria (LAB) became predominant. L. farciminis overcame L. curvatus and remained dominant until the end of propagations for both sourdoughs. At 21 °C, Bacillus, Clostridium, Pseudomonas, and Enterobacteriaceae were gradually inhibited. At the end of propagation, SD1 harbored only LAB. Otherwise, the temperature of 30 °C favored the persistence of atypical bacteria in SD2, as Pseudomonas and Enterobacteriaceae. Therefore, the temperature of 21 °C was more suitable for sourdough propagation in Brazil. This study enhanced the knowledge of temperature's influence on microbial assembly and contributed to the elucidation of sourdough microbial communities in Brazil.

Complete Genome Sequence of Turicibacter sp. Strain H121, Isolated from the Feces of a Contaminated Germ-Free Mouse.

Turicibacterbacteria are commonly detected in the gastrointestinal tracts and feces of humans and animals, but their phylogeny, ecological role, and pathogenic potential remain unclear. We present here the first complete genome sequence ofTuricibactersp. strain H121, which was isolated from the feces of a mouse line contaminated following germ-free derivation.

Development of a simple and rapid Agrobacterium tumefaciens-mediated transformation system for the entomopathogenic fungus Metarhizium anisopliae var. acridum.

AIMS: To examine the ability of Agrobacterium to attach to Metarhizium anisopliae var. acridum strain CG423 under co-cultivation and to develop an Agrobacterium-mediated method of gene delivery into strain CG423, a promising agent for biological control of grasshoppers. METHODS AND RESULTS: The co-cultivation of Agrobacterium tumefaciens and M. anisopliae var. acridum was analysed under scanning electron microscopy. We observed that Agrobacterium attached to and formed aggregates around Metarhizium conidia and germ tubes. We also observed the occurrence of fibril-like structures connecting neighbouring bacterial-fungal cells. The Agrobacterium-mediated transformation was applied using two binary vectors carrying a benomyl resistance gene as a selection marker. The efficiency of transformation was up to 53 transformants per 10(5) target conidia. High mitotic stability of the transformants (89-97%) was demonstrated after five successive transfers on non-selective media. Molecular analysis revealed the occurrence of high frequency of gene conversion. CONCLUSIONS: In our study, we report that A. tumefaciens strain AGL-1 attaches to and genetically transforms the entomopathogenic fungus Metarhizium anisopliae var. acridum. SIGNIFICANCE AND IMPACT OF THE STUDY: We report for the first time, the attachment of Agrobacterium to fungal cells opening new avenues for the study of this essential step of the T-DNA transfer process. Considering the efficiency of the transformation protocol herein described, this is a useful tool for gene disruption in M. anisopliae var. acridum.

Transformation of the entomopathogenic fungus Paecilomyces fumosoroseus with Agrobacterium tumefaciens.

AIMS: To test the suitability of the Agrobacterium tumefaciens-mediated transformation (AMT) method with Paecilomyces fumosoroseus, a fungal pathogen that causes diseases in a wide range of insects including whiteflies. METHODS AND RESULTS: Conidia of P. fumosoroseus were successfully transformed to hygromycin B resistance using the hph gene of Escherichia coli as the selectable marker. Transformation frequencies were 58.3 +/- 18.5, 98.3 +/- 24.8 and 169.7 +/- 35.5 (+/-SEM) transformants per 10(5), 10(6) and 10(7) target conidia respectively. After confirmation by PCR, transformants were subjected to Southern analysis, and the results revealed that 45% (four of nine) of the transformants contained single-copy integration of the T-DNA. CONCLUSIONS: In our AMT system, we efficiently transformed conidia of P. fumosoroseus. The employment of this method circumvents time-consuming protoplast preparation and allows the isolation of transformants containing single-copy integration of the T-DNA. SIGNIFICANCE AND IMPACT OF THE STUDY: Considering the efficiency of Ag. tumefaciens-mediated transformation, this method represents a useful tool for insertional mutagenesis to characterize genes that are important for the pathogenicity of P. fumosoroseus.