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The use of industrial wastes rich in mineral nutrients and carbon sources to increase the final microalgal biomass and lipid yield at a low cost is an important strategy to make algal biofuel technology viable. Using strains from the microalgal collection of the Université de Montréal, this report shows for the first time that microalgal strains can be grown on xylose, the major carbon source found in wastewater streams from pulp and paper industries, with an increase in growth rate of 2.8 fold in comparison to photoautotrophic growth, reaching up to µ=1.1/day. On glycerol, growth rates reached as high as µ=1.52/day. Lipid productivity increased up to 370% on glycerol and 180% on xylose for the strain LB1H10, showing the suitability of this strain for further development for biofuels production through mixotrophic cultivation.Final Version available online at: http://dx

Algal cultivation at high latitudes is challenged by the relatively low annual solar flux. One possible scenario to overcome this limitation is the use of mixotrophic growth to potentially boost biomass and lipid production. Here the effect of glycerol addition on the growth and lipid production by twelve indigenous microalgae was examined. The results show that there is considerable strain dependent variation in the maximum growth rate under mixotrophic conditions with the addition of glycerol causing in some cases up to a 2.4-fold increase in growth rate and a up to a 1.9-fold increase in biomass. In addition, glycerol increased total lipid production 40-60% in some strains. These results also show the value in screening culture collections for desired traits independent of strain identification since here one (PCH02) of the five Chlorella strains showed a large increase in lipid with glycerol.

Background Cooling towers are a major source of large community-associated outbreaks of Legionnaires’ disease, a severe pneumonia. This disease is contracted when inhaling aerosols that are contaminated with bacteria from the genus Legionella, most importantly Legionella pneumophila. How cooling towers support the growth of this bacterium is still not well understood. As Legionella species are intracellular parasites of protozoa, it is assumed that protozoan community in cooling towers play an important role in Legionella ecology and outbreaks. However, the exact mechanism of how the eukaryotic community contributes to Legionella ecology is still unclear. Therefore, we used 18S rRNA gene amplicon sequencing to characterize the eukaryotic communities of 18 different cooling towers. The data from the eukaryotic community was then analysed with the bacterial community of the same towers in order to understand how each community could affect Legionella spp. ecology in cooling towers. Results We identified several microbial groups in the cooling tower ecosystem associated with Legionella spp. that suggest the presence of a microbial loop in these systems. Dissolved organic carbon was shown to be a major factor in shaping the eukaryotic community and may be an important factor for Legionella ecology. Network analysis, based on co-occurrence, revealed that Legionella was correlated with a number of different organisms. Out of these, the bacterial genus Brevundimonas and the ciliate class Oligohymenophorea were shown, through in vitro experiments, to stimulate the growth of L. pneumophila through direct and indirect mechanisms. Conclusion Our results suggest that Legionella ecology depends on the host community, including ciliates and on several groups of organisms that contribute to its survival and growth in the cooling tower ecosystem. These findings further support the idea that some cooling tower microbiomes may promote the survival and growth of Legionella better than others.

20Legionnaire's Disease (LD) is a severe pneumonia caused by Legionella pneumophila. Cooling 21 towers are the main source of L. pneumophila during large outbreaks. Colonization, survival, and 22 proliferation of L. pneumophila in cooling towers are necessary for outbreaks to occur. These 23 steps are affected by chemical and physical parameters of the cooling tower environment. We 24 hypothesize that the bacterial community residing in the cooling tower could also affect the 25 presence of L. pneumophila. A 16S rRNA targeted amplicon sequencing approach was used to 26 study the bacterial community of cooling towers and its relationship with the Legionella spp. and 27 L. pneumophila communities. The results indicated that the water source shaped the bacterial 28 community of cooling towers. Several taxa were enriched and positively correlated with 29 Legionella spp. and L. pneumophila. In contrast, Pseudomonas showed a strong negative 30 correlation with Legionella spp. and several other genera. Most importantly, continuous chlorine 31 application reduced microbial diversity and promoted the presence of Pseudomonas creating a 32 non-permissive environment for Legionella spp. This suggests that disinfection strategies as well 33 as the resident microbial population influences the ability of Legionella spp. to colonize cooling 34 towers. 35 36 37 14]. From 2000 to 2014, the CDC reported an increase of 286% in cases of Legionellosis (LD 50 and Pontiac fever) in the USA [15]. This increase is likely due to increasing population in urban 51 areas, improvements in surveillance methods, aging populations, and climate change [13]. 52Legionella is now the main cause of death due to waterborne diseases in the US [16]. 53 54 Several steps are needed for a tower to become the source of an outbreak of LD. First, the tower 55 must be seeded with L. pneumophila. During operation, the water lost through evaporation is 56 replenished either with municipal water, onsite well water or available surface water, which may 57 be the source of L. pneumophila [17, 18]. Next, L. pneumophila must survive and proliferate in 58 the cooling tower environment. Encountered stresses include low quantity of nutrients, 59 disinfectants, and competing microbes [19, 20]. L. pneumophila can survive up to several months 60 in oligotrophic water while retaining infectivity [21]. Multiple factors may affect the prevalence 61 of Legionella and its hosts in cooling towers including operational factors, temperature, water 62 quality, the age of the equipment, the use of biocides (dosage, type and application schedule and 63 residual concentration), and elevated bacterial indicators such as heterotrophic plate counts 64 (HPC) [22, 23, 24, 25]. In addition, biofilms offer protection against disinfectants, while also 65 providing nutrients and host cells [26, 27, 28, 29, 19]. While it is not clear if L. pneumophila can 66 grow in biofilms independently of protozoan host cells, several studies indicate that this might be 67 possible [30, 28, 31]. Moreover,...