Biology subjects

Christie-Oleza, J. A.

Publications and source records attributed to Christie-Oleza, J. A..

7 recordsLinked to original sources

bioRxiv2025

Metabolic redundancy is required for microbial polyethylene assimilation

Polyethylene (PE) is amongst the most recalcitrant synthetic polymers, and only a limited number of microbes have been shown to utilise it as their sole carbon and energy source. Here, we investigated the metabolic basis enabling the efficient assimilation of PE oxidised scission products and its prevalence in microbial communities naturally colonising plastic surfaces. Metabolomic profiling of weathered PE (W-PE) leachates revealed a highly diverse pool of oxidised aliphatic compounds varying in chain length and oxidation state. Different plastic-degrading bacteria consumed this complex mix of metabolites to distinct extents, with consumption efficiency positively correlating with the number of redundant genes associated with the {beta}-oxidation pathway in their genomes. Comparative proteomic analysis of two Alcanivorax species exhibiting contrasting PE-leachate consumption capabilities confirmed that this functional redundancy was fully activated in response to the chemically complex PE-derived substrate pool. In contrast, it remained largely uninduced in the presence of the single, structurally simple alkane hexadecane. Hence, our results indicate that efficient PE assimilation requires a broad and redundant enzymatic repertoire capable of funnelling structurally diverse oxidised aliphatic intermediates through {beta}-oxidation. Metagenomic analysis of plastisphere communities further revealed enrichment of fatty acid degradation genes in biofilms colonising both pristine and weathered PE--as expected more strongly in W-PE--compared with wood and surrounding water controls, supporting the ecological relevance of this mechanism for PE biodegradation. Together, these findings identify {beta}-oxidation metabolic redundancy as a key trait underpinning microbial PE assimilation and suggest that plastic degradation may be occurring under natural environmental conditions.

microbiology↗

bioRxiv2025

Type IV pili increase phage encounter in marine cyanobacteria

Type IV pili are extracellular bacterial appendages with diverse functions, including biofilm formation, motility, conjugation, transformation, pathogenicity, and secretion. In planktonic marine cyanobacteria, they also enhance buoyancy and protect against grazing, yet their consequences for the oceanic carbon pump and microbial loop remain poorly understood. Pili production in dilute marine ecosystems entails ecological trade-offs, including high nutrient investment and, as we show here, increased vulnerability to phage infection. Using high-resolution electron microscopy, we observed cyanophages attaching along the entire length of extracellular pili, indicating that these filaments act as structural amplifiers of viral encounter in diffusion-limited environments. While piliated and non-piliated Synechococcus exhibited similar mortality in isolation, competition assays revealed a strong selective disadvantage for piliated cells, which were more rapidly depleted in mixed populations. This effect was most pronounced for cyanophage S-CAM7, which displayed higher pili-binding affinity and drove competitive exclusion of piliated hosts. To extend these findings to natural settings, we analysed single-cell amplified genomes (SAGs) observing pili genes encoded by 14.7% of total cyanobacterial SAGs. This proportion increased to 28.1% in virally infected SAGs (virocells; representing 3.8% of the total cyanobacterial SAGs), consistent with encounter-driven susceptibility of piliated cells in the environment. Together, our results identify type IV pili as double-edged structures: while conferring ecological advantages, they expose cells to viral attack by increasing encounter probability when pilus-attached phage are transport to the cell surface during pili retraction. This fitness cost may help explain the patchy distribution of pili in natural populations and the extreme sequence variability of pilins, reflecting an ongoing evolutionary arms race with phage.

microbiology↗

bioRxiv2021

Cell size matters: nano- and micro-plastics preferentially drive declines of large marine phytoplankton due to co-aggregation

Marine plastic pollution represents a key environmental concern. Whilst ecotoxicological data for plastic is increasingly available, its impact upon marine phytoplankton remains unclear. Owing to their predicted abundance in the marine environment and likely interactions with phytoplankton, here we focus on the smaller fraction of plastic particles ([~]50 nm and [~]2 {micro}m polystyrene spheres). Exposure of natural phytoplankton communities and laboratory cultures revealed that plastic exposure does not follow traditional trends in ecotoxicological research, since large phytoplankton appear particularly susceptible towards plastics exposure despite their higher surface-to-volume ratios. Cell declines appear driven by hetero-aggregation and co-sedimentation of cells with plastic particles, recorded visually and demonstrated using confocal microscopy. As a consequence, plastic exposure also caused disruption to photosynthetic functioning, as determined by both photosynthetic efficiency and high throughput proteomics. Negative effects upon phytoplankton are recorded at concentrations orders of magnitude above those estimated in the environment. Hence, it is likely that impacts of NPs and MPs are exacerbated at the high concentrations typically used in ecotoxicological research (i.e., mg L-1).

ecology↗

bioRxiv2020

Phytoplankton trigger the production of cryptic metabolites in the marine actinobacteria Salinispora tropica

Bacteria from the Actinomycete family are a remarkable source of natural products with pharmaceutical potential. The discovery of novel molecules from these organisms is, however, hindered because most of the biosynthetic gene clusters (BGCs) encoding these secondary metabolites are cryptic or silent and are referred to as orphan BGCs. While co-culture has proven to be a promising approach to unlock the biosynthetic potential of many microorganisms by activating the expression of these orphan BGCs, it still remains an underexplored technique. The marine actinobacteria Salinispora tropica, for instance, produces valuable compounds such as the anti-cancer molecule salinosporamide A but half of its putative BGCs are still orphan. Although previous studies have looked into using marine heterotrophs to induce orphan BGCs in Salinispora, the potential impact of co-culturing marine phototrophs with Salinispora has yet to be investigated. Following the observation of clear antimicrobial phenotype of the actinobacterium on a range of phytoplanktonic organisms, we here report the discovery of novel cryptic secondary metabolites produced by S. tropica in response to its co-culture with photosynthetic primary producers. An approach combining metabolomics and proteomics revealed that the photosynthate released by phytoplankton influences the biosynthetic capacities of S. tropica with both production of new molecules and the activation of orphan BGCs. Our work pioneers the use of phototrophs as a promising strategy to accelerate the discovery of novel natural products from actinobacteria. ImportanceThe alarming increase of antimicrobial resistance has generated an enormous interest in the discovery of novel active compounds. The isolation of new microbes to untap novel natural products is currently hampered because most biosynthetic gene clusters (BGC) encoded by these microorganisms are not expressed under standard laboratory conditions, i.e. mono-cultures. Here we show that co-culturing can be an easy way for triggering silent BGC. By combining state-of-the-art metabolomics and high-throughput proteomics, we characterized the activation of cryptic metabolites and silent biosynthetic gene clusters in the marine actinobacteria Salinispora tropica by the presence of phytoplankton photosynthate. We further suggest a mechanistic understanding of the antimicrobial effect this actinobacterium has on a broad range of prokaryotic and eukaryotic phytoplankton species and reveal a promising candidate for antibiotic production.

microbiology↗

bioRxiv2018

Riding the wave of genomics, to investigate aquatic coliphage diversity and activity

Bacteriophages infecting Escherichia coli have been used as a proxy for faecal matter and water quality from a variety of environments. However, the diversity of coliphages that are present in seawater remains largely unknown, with previous studies largely focusing on morphological diversity. Here, we isolated and characterised coliphages from three coastal locations in the UK and Poland. This revealed a surprising genetic diversity, with comparative genomics and phylogenetic analysis of phage isolates facilitating the identification of putative new species within the genera RB69virus and T5virus and a putative new genus within the subfamily Tunavirinae. Furthermore, by combining this genomic data with proteomic and host range analyses a number of phage structural proteins were identified, one of which is likely to be responsible for the observed differences in host range.

microbiology↗

bioRxiv2018

Artificial selection of microbial communities to enhance degradation of recalcitrant polymers

Recalcitrant polymers are widely distributed in the environment. This includes natural polymers, such as chitin, but synthetic polymers are becoming increasingly abundant, for which biodegradation is uncertain. Distribution of labour in microbial communities commonly evolves in nature, particularly for arduous processes, suggesting a community may be better at degrading recalcitrant compounds than individual microorganisms. Artificial selection of microbial communities with better degradation potential has seduced scientists for over a decade, but the method has not been systematically optimised nor applied to polymer degradation. Using chitin as a case study, we successfully selected for microbial communities with enhanced chitinase activities but found that continuous optimisation of incubation times between selective generations was of utmost importance. The analysis of the community composition over the entire selection process revealed fundamental aspects in microbial ecology: when incubation times between generations were optimal, the system was dominated by Gammaproteobacteria, main bearers of chitinase enzymes and drivers of chitin degradation, before being succeeded by cheating, cross-feeding and grazing organisms.\n\nImportanceArtificial selection is a powerful and atractive technique that can enhance the biodegradation of a recalcitrant polymer and other pollutants by microbial communities. We show, for the first time, that the success of artificially selecting microbial communities requires an optimisation of the incubation times between generations when implementing this method. Hence, communities need to be transferred at the peak of the desired activity in order to avoid community drift and replacement of the efficient biodegrading community by cheaters, cross-feeders and grazers.

microbiology↗

bioRxiv2018

Manganese oxide biomineralization is a social trait protecting against nitrite toxicity

Manganese bio-mineralization by oxidation is a costly but, still, widespread process among bacteria and fungi. While certain potential advantages of manganese oxidation have been suggested, to date there is no conclusive experimental evidence for, how and if this process impacts microbial fitness in the environment. Here we show how a model organism for manganese oxidation, Roseobacter sp. AzwK-3b, is growth-inhibited by nitrite, and that this inhibition is mitigated when manganese is added to the culture medium. We show that manganese-mediated mitigation of nitrite-inhibition is dependent on the culture inoculum size, with larger inocula being able to withstand higher concentrations of nitrite stress. Furthermore, the bio-mineralized manganese oxide (MnOX) forms granular precipitates in the culture, rather than sheaths around individual cells. These findings support the notion that MnOX is a shared community product that improves the cultures survival against nitrite-stress. We show that the mechanistic basis of the MnOX effect involves both its ability to catalyze nitrite oxidation into (non-toxic) nitrate under physiological conditions, and its potential role in influencing redox chemistry around reactive oxygen species (ROS). Taken together, these results provide for the first direct evidence of improved microbial fitness by MnOX deposition in an ecological setting, i.e. mitigation of nitrite toxicity, and point to a key role of MnOX in handling stresses arising from ROS. These findings could be of general relevance for all organisms oxidizing manganese, allowing them to offset costs associated with extracellular bio-mineralization.

microbiology↗