Transcriptomic response of an Antarctic yeast Rhodotorula sp. USM-PSY62 to temperature changes

Aims@#Rhodotorula sp. (USM-PSY62) is a psychrophilic yeast isolated from Antarctic sea ice that grows optimally at 15°C. The inevitable global warming poses many challenges to the microbial community in Antarctica. Therefore, this studywas conceptualized to observe how USM-PSY62 adapted to fluctuations in temperature.@*Methodology and results @#Rhodotorula sp. (USM-PSY62) was grown in YPD broth until the mid-log phase. Then, the culture was transferred to four different temperatures, specifically at 0 °C, 5 °C, 15 °C and 21 °C for 24 h. Then, the RNA was extracted, sequenced and analysed. During cold adaptation, an elevated transcription of the CorA magnesium transporter gene in USM-PSY62 indicated a higher requirement for magnesium ions to gain additional enzyme cofactors or maintain cytoplasmic fluidity. The HepA homologue coding for DNA/RNA helicase was also over-expressed with log fold change 2.89 in cold conditions possibly to reorganize secondary structures of DNA and RNA. An up-regulation of the catalase gene was also observed, reflecting an increment in the concentration of reactive oxygen species and fluctuations in the associated antioxidant system. The YOP1 gene, which encodes a membrane protein associated with protein transport and membrane traffic, was the most down-regulated, with log2 fold change values of -6.93 lower under cold shock conditions. The genes responsible for the structural maintenance of chromosome (SMC) have a -8.80 in expression log2 fold change, indicating the gene was down-regulated when the temperature was shifted to 0 °C. Upon cold shock, the gene for heat shock factor protein 1 (HSF1) was also down-regulated with a log2 fold change value of - 5.86. Hsf1 is a transcriptional regulator which regulates the heat shock responses.@*Conclusion, significance and impact of study: @#In conclusion, the transcriptomic responses demonstrated by Rhodotorula sp. USM-PSY62 characterized critical physiological and biochemical compensatory mechanisms especially cellular processes and signalling, information storage and processing, and metabolism to survive at low and high temperatures. This study provides valuable data for industry, especially in the usage of molecular chaperones.

Unveiling the multifaceted microbial strategies: Insights into ecological adaptations and interactions

@#Microorganisms, such as spanning bacteria, archaea and fungi, were ubiquitous and played pivotal roles in shaping ecosystems. This review offered a comprehensive investigation into the multifaceted strategies employed by microorganisms to thrive and adapt within complex ecological niches. Key themes explored in this review encompassed microbial defence mechanisms, biofilm formation, quorum sensing and altruistic behaviours. Microbial defence mechanisms were scrutinized, with a focus on bacteriocin production. Despite the costs associated with production, bacteriocins served as potent weapons that selectively targeted closely related strains, reducing competition and conferring indirect benefits to the producer's genetic kin. Biofilm formation, a critical facet of microbial survival, was discussed in detail. These structured microbial communities encased in self-secreted extracellular matrices provided structural support and protection, demonstrating their significance in diverse ecological contexts. The review further delved into the evolutionary implications of quorum sensing and altruism within microbial communities. Quorum sensing, a mechanism that allowed population density-dependent communication and cooperation, was revealed as essential for microbial survival. In conclusion, this review enhanced our understanding of the intricate strategies microorganisms employed for survival, adaptation and competition in intricate ecosystems. By shedding light on these mechanisms, it advanced our comprehension of microbial community dynamics and their indispensable roles in diverse environments.

Transposable elements: Uniqueness and applications

@#The study of transposable genetic elements, a cornerstone of molecular genetics, offers profound insights into the dynamic nature of genetic material. This exploration encompasses various types found in bacteria, including insertion sequences, composite and non-composite transposons. These elements are instrumental in shaping bacterial genomes by facilitating the movement of genetic information, driving evolution and contributing to genetic diversity. Understanding the mechanisms of transposition is essential for unravelling the intricate processes governing genetic rearrangements. Replicative and conservative transposition mechanisms, exemplified by the Tn3 family and phage Mu, illustrate the remarkable adaptability of these systems in reshaping genomes. However, it is the transposon Tn5 that steals the spotlight as a versatile molecular genetics tool. Tn5's transposition mechanism, characterized by precise control over gene expression, translational regulation, protein localization and the induction of conditional mutations, empowers researchers to dissect gene regulation intricacies with unprecedented accuracy. Transposable genetic elements, epitomized by Tn5, are indispensable instruments in molecular genetics. They allow researchers to navigate the intricate landscape of genetics, exploring gene regulation, protein function, and genetic diversity with unparalleled precision. These elements continue to be at the forefront of molecular genetics research, driving innovations that deepen our understanding of the fundamental mechanisms governing life's genetic code.

Emericella nidulans (4DP5), Cladosporium herbarum (7DF12) and Bacillus subtilis improve the nutritional value of palm kernel cake (PKC) through solid-state fermentation (SSF)

Aims@#Palm kernel cake (PKC) is a high-protein, high-energy food that is widely utilized in the animal feed business. However, the high fibre and limited amino acid content of untreated PKC were the main issues for it to be used as animal feed, particularly in non-ruminants. To improve the quality of PKC, this study combined the use of solid-state fermentation (SSF) and consortia of fungi and bacteria to treat the PKC.@*Methodology and results@#Two fungi, Emericella nidulans (4DP5) and Cladosporium herbarum (7DF12) and three strains of bacteria, Bacillus subtilis, which were active mannanase producers, were used in different combinations to reduce the hemicellulose content and improve the crude protein content of PKC in a lab-scale solid-state fermentation. PKC inoculated separately with five types of mixed culture treatments were allowed to ferment. The fermentation conditions were 20% inoculum (w/v), 85-92% humidity, pH 7.0 and PKC particle size 0.8 mm. PKC treatments with two fungi, E. nidulans (4DP5) and C. herbarum (7DF12), as well as a fungus-bacterium combination, E. nidulans (4DP5) and B. subtilis, outperformed the other three treatments. The crude protein levels were increased by 3.34% and 1.86%, respectively, due to these treatments. Furthermore, the level of aflatoxins produced increased marginally but remained within the permissible limits.@*Conclusion, significance and impact of study@#The treated PKC has more sugar and crude protein and less than 20 parts per billion (ppb) of aflatoxin, making it appropriate for animal consumption. The SSF technique of combining fungi and Bacilli enhanced the nutritional and market value of PKC substantially, which can be upscaled.

Bacterial diversity on wild shrimp post larvae in a mangrove biodiversity hotspot

Aims@#This study aims to assess the impact of anthropogenic activities on shrimp microbiome in a biodiverse mangrove forest ecosystem, along the Merbok River, Kedah, Malaysia.@*Methodology and results@#To assess the impacts, a microbiome study of wild post larvae shrimps along the river was conducted as a health indicator of the shrimp hosts which in turn would reflect the river conditions. A 16S rRNA gene amplicon sequencing of the wild post larvae shrimp microbiomes sampled across areas of varying human activities was conducted. Samples were obtained from four sites ranging from upstream river habitat to downstream brackish water towards the marine coast. Individuals detected from the sequence were then counted and their relative abundance of bacterial diversity were compared. All abundances are up to 100% and the diversity indices were calculated using proportions of each species. The Operational Taxonomy Unit (OTUs) were obtained by using USEARCH and UPARSE software. Twenty-eight bacterium phyla were detected, dominated by phyla Proteobacteria, Actinobacteria, Firmicutes and Bacteroidetes at each site. Eighteen families were dominant at each site with Streptomycetaceae being the major abundant. At the genus level, the most abundant genera were Streptomyces sp., Mesorhizobium sp., Rhizobium sp., Bacillus sp. and Pseudomonas sp.@*Conclusion, significance and impact of study@#In general, the diversity of opportunistic and coliform bacteria was low. Thus, despite being exposed to various levels of human activities, the Merbok River and its mangrove surroundings still serve as a good spawning and nursery sites of shrimps and presumably other inhabitants.

Discovering the thermophiles microbial diversity of Malaysian hot spring in Ulu Slim, Perak

@#Aims: Hot springs are major sources of useful thermophilic microbes. Our study therefore aimed at documenting and analysing the microbial communities at Ulu Slim hot spring in Perak, Malaysia, for bacteria with beneficial enzymes for industrial applications. Methodology and results: The study sampled water and sediment materials from the Ulu Slim hot spring at two sublocations of different temperatures, 45 °C and 72 °C. The samples were then extracted for genomic DNA, followed by paired-end metagenome sequencing using prokaryotic-conserved, locus specific primers for 16S rRNA V3 and V4 domains, and Illumina MiSeq (2  300) sequencing platform. Raw data were optimized using Trimmomatic and FLASH, followed by operational taxonomy units (OUT) determination and clustering. 16S rRNA gene sequences were then analysed against Silva (SSU123) 16S rRNA gene databases for phylum and genus classifications. Data analysis showed relevant alignment of present bacteria phyla against data from a previous study on Ulu Slim hot springhead, though the different sample temperatures significantly affected phylum and genus composition. Our study also confirmed the presence of a site-specific genus, Fervidobacteria, which are anaerobic bacteria with a unique ability in degrading keratin. Conclusion, significance and impact of study: The study further completes and complement the findings on microbial communities at the Ulu Slim hot spring. The findings help to reveal the associations between microbes and environmental factors at thermophilic locations, as well as potential thermostable enzymes like lipase and amylase that can be isolated from thermophilic sample as they are indispensable for industry.

The potential use of prodigiosin as a shrimp feed additive and its dynamic influence on the shrimp gut microbial community – an in vitro gut model

Aims@#A simple in vitro model system was applied in this study assessing the dynamics of the microbial community associated with the shrimp gut system to understand the changes that influence dietary variables. @*Methodology and results@#The diversity and abundance of microbiome were monitored within two different treatment slurries inoculated with shrimp faecal samples as to mimic the effect of diet manipulation, and 16S rRNA gene of MiSeq Illumina-based sequencing was applied. The different diets tested were a commercial standard diet and a prodigiosin added diet. There was very clear separation between the commercial standard diet and prodigiosin added diet as revealed by the total viable counts (TVC) and sequencing data. It suggested that the microbial community of the shrimp gut system exhibited a dynamic response with the treatments and allochthonous bacterial present. The prodigiosin added diet was clearly separated from the commercial standard diet serving as a potential shrimp feed additive. The sequencing data analysis showed that members of the genera Vibrio, Shigella and Photobacterium became predominant on the commercial standard diet treatment. The prodigiosin-added diet treatments indicated an abundance of members of the genera Micrococcus, Arthrobacter, and Shigella. @*Conclusion, significance and impact of study@#In vitro model system-based testing of diets could be a useful method to determine the potential effect of diet manipulation on shrimp gut system microbiome members.