Exploring the onset of B12-based mutualisms using a recently evolved Chlamydomonas auxotroph and B12-producing bacteria

Cobalamin (vitamin B12), is a cofactor for crucial metabolic reactions in multiple eukaryotic taxa, including major primary producers such as algae, and yet only prokaryotes can produce it. Many bacteria can colonise the algal phycosphere, forming stable communities that gain preferential access to exudates and in return provide compounds, such as B12. Extended coexistence can then drive gene loss, leading to greater algal-bacterial interdependence. In this study, we investigate how a recently evolved B12-dependent strain of Chlamydomonas reinhardtii, metE7, forms a mutualism with certain bacteria, including the rhizobium Mesorhizobium loti and even a strain of the gut bacterium E. coli engineered to produce cobalamin. Although metE7 was supported by B12 producers, its growth in co-culture was slower than the B12-independent wild-type, suggesting that high bacterial B12 provision may be necessary to favour B12 auxotrophs and their evolution. Moreover, we found that an E. coli strain that releases more B12 makes a better mutualistic partner, and although this trait may be more costly in isolation, greater B12 release provided an advantage in co-cultures. We hypothesise that, given the right conditions, bacteria that release more B12 may be selected for, particularly if they form close interactions with B12-dependent algae.

What if vaccines do not prevent infection?

Aims of the study Vaccines are considered to be our greatest hope of defeating SARS-CoV-2. However, before we claim victory, there are some important questions that are in need of an urgent answer. In this paper we address a particularly relevant one, which unfortunately has not attracted much attention: whether approved vaccines provide us with sterilizing immunity (or to what concrete level). Methods used to conduct the study This study was based on the revision of the existing academic literature. Results of the study The capacity of approved vaccines to provide sterilizing immunity is key to designing our vaccination policies in an optimal way. We propose ways to obtain this knowledge and we assess the consequences that a lack of sufficient immunity would bring to publc health policies. Conclusions drawn from the study and clinical implications If further evidence proves that vaccines do not provide sterilizing immunity, prioritization strategies should introduce changes by providing preferential access to vulnerable populations instead of health care professionals or caregivers working in nursing homes. Policies aimed at promoting adherence to vaccination should consider that altruistic incentives would clearly diminish. In addition, policy makers should be aware that, in general, reaching herd immunity could take much longer than expected.

Spatial organization in microbial range expansion emerges from trophic dependencies and successful lineages

Evidence suggests that bacterial community spatial organization affects their ecological function, yet details of the mechanisms that promote spatial patterns remain difficult to resolve experimentally. In contrast to bacterial communities in liquid cultures, surface-attached range expansion fosters genetic segregation of the growing population with preferential access to nutrients and reduced mechanical restrictions for cells at the expanding periphery. Here we elucidate how localized conditions in cross-feeding bacterial communities shape community spatial organization. We combine experiments with an individual based mathematical model to resolve how trophic dependencies affect localized growth rates and nucleate successful cell lineages. The model tracks individual cell lineages and attributes these with trophic dependencies that promote counterintuitive reproductive advantages and result in lasting influences on the community structure, and potentially, on its functioning. We examine persistence of lucky lineages in structured habitats where expansion is interrupted by physical obstacles to gain insights into patterns in porous domains.

A bacterial endophyte exploits chemotropism of a fungal pathogen for plant colonization

Soil-inhabiting fungal pathogens use chemical signals released by roots to direct hyphal growth towards the host plant. Whether other soil microorganisms exploit this capacity for their own benefit is currently unknown. Here we show that the endophytic rhizobacterium Rahnella aquatilis locates hyphae of the root-infecting fungal pathogen Fusarium oxysporum through pH-mediated chemotaxis and uses them as highways to efficiently access and colonize plant roots. Secretion of gluconic acid (GlcA) by R. aquatilis in the rhizosphere leads to acidification and counteracts F. oxysporum-induced alkalinisation, a known virulence mechanism, thereby preventing fungal infection. Genetic abrogation or biochemical inhibition of GlcA-mediated acidification abolished biocontrol activity of R. aquatilis and restored fungal infection. These findings reveal a new way by which bacterial endophytes hijack hyphae of a fungal pathogen in the soil to gain preferential access to plant roots, thereby protecting the host from infection.

Potential female mate choice in a male dominated system: the female capybara, Hydrochoerus hydrochaeris

Capybaras, Hydrochoerus hydrochaeris (Rodentia: Caviidae: Hydrochoerinae), show a strict social hierarchy among males, wherein the top-ranking male gains preferential access to females. Despite minimal sexual size dimorphism, males have a prominent scent gland on their snouts that is greatly reduced in the females. Top-ranking males have a larger gland and mark more frequently than subordinate males. This species also shows a moderately complex courtship that seems to be modulated by female behavior. In this study, we evaluated several components of courtship, as well as the females’ interactions with males during and outside courtship, in relation to the hierarchy rank of males. We found that subordinate males engaged in longer courtships than top-ranking males. However, there was no difference in the number of mount attempts or the success rate of these mounts as a function of the social status of the male, despite the longer courtship performed by subordinate males in comparison to top-ranking males. Outside courtship, females directed the same number of social interactions to males regardless of status. However, during courtship, females avoided copulation by subordinate males both directly and indirectly by encouraging courtship disruption by higher-ranking males. Females’ avoidance of subordinates may force these males to invest a higher amount of effort in courtships, thus engaging in longer courtships, yet achieving similar mount success as top-ranking males. We show that the original assumption of male hierarchy as the main mechanism of reproductive distribution is incomplete, and female mate choice plays an important role in determining which males reproduce.

Reforms and Global Economic Integration of the Indian Economy

Nagesh Kumar brings out the reforms pursued since 1991 have deepened global integration of the Indian economy. Opportunities for product and market diversification remain to be fully exploited to sustain export growth and create more jobs. Despite healthy trade surpluses earned by services as India emerged as a global hub for ICT outsourcing, the balance of payment situation continues to face occasional pressures related to oil prices fluctuations. Export competitiveness needs to be strengthened through appropriate exchange rate management and opportunities for strategic import substitution need to be exploited by leveraging India’s large domestic market size using industrial policy measures, such as Make-in-India. While farsighted policies have led India becoming a part of emerging broader regional economic arrangement, Indian industry has yet to learn to exploit the opportunities provided by preferential access to East Asian markets rather than passively grant market access.

Towards a Market for Land in India

Years after the Government of India (GOI) has notified the Right to Fair Compensation and Transparency in Land Acquisition, Rehabilitation and Resettlement Act, 2013 there is still uncertainty on how land should be acquired. India still has no national market for land. The absence of such a market makes it difficult to set an efficient and transparent price for land. Its absence makes those who have the smallest parcels of it more vulnerable as the cost of inefficiency are borne by them disproportionately reducing the welfare outcomes for the economy. Also government agencies hold the largest block of land in the country, not as a sovereign entity but as a business entity. These abundant holdings create incentive for interested parties to game the system to get preferential access to those land parcels, instead of buying the same at a discovered price from the market. Thus, the policy of non-market-based allocation of land breeds corruption.