Conserved transcriptional connectivity of regulatory T cells in the tumor microenvironment informs new combination cancer therapy strategies.

While regulatory T (Treg) cells are traditionally viewed as professional suppressors of antigen presenting cells and effector T cells in both autoimmunity and cancer, recent findings of distinct Treg cell functions in tissue maintenance suggest that their regulatory purview extends to a wider range of cells and is broader than previously assumed. To elucidate tumoral Treg cell 'connectivity' to diverse tumor-supporting accessory cell types, we explored immediate early changes in their single-cell transcriptomes upon punctual Treg cell depletion in experimental lung cancer and injury-induced inflammation. Before any notable T cell activation and inflammation, fibroblasts, endothelial and myeloid cells exhibited pronounced changes in their gene expression in both cancer and injury settings. Factor analysis revealed shared Treg cell-dependent gene programs, foremost, prominent upregulation of VEGF and CCR2 signaling-related genes upon Treg cell deprivation in either setting, as well as in Treg cell-poor versus Treg cell-rich human lung adenocarcinomas. Accordingly, punctual Treg cell depletion combined with short-term VEGF blockade showed markedly improved control of PD-1 blockade-resistant lung adenocarcinoma progression in mice compared to the corresponding monotherapies, highlighting a promising factor-based querying approach to elucidating new rational combination treatments of solid organ cancers.

Transcriptional Basis of Mouse and Human Dendritic Cell Heterogeneity.

Dendritic cells (DCs) play a critical role in orchestrating adaptive immune responses due to their unique ability to initiate T cell responses and direct their differentiation into effector lineages. Classical DCs have been divided into two subsets, cDC1 and cDC2, based on phenotypic markers and their distinct abilities to prime CD8 and CD4 T cells. While the transcriptional regulation of the cDC1 subset has been well characterized, cDC2 development and function remain poorly understood. By combining transcriptional and chromatin analyses with genetic reporter expression, we identified two principal cDC2 lineages defined by distinct developmental pathways and transcriptional regulators, including T-bet and RORγt, two key transcription factors known to define innate and adaptive lymphocyte subsets. These novel cDC2 lineages were characterized by distinct metabolic and functional programs. Extending our findings to humans revealed conserved DC heterogeneity and the presence of the newly defined cDC2 subsets in human cancer.

Gradients of the signaling lipid S1P in lymph nodes position natural killer cells and regulate their interferon-γ response.

The lymph node periphery is an important site for many immunological functions, from pathogen containment to the differentiation of helper T cells, yet the cues that position cells in this region are largely undefined. Here, through the use of a reporter for the signaling lipid S1P (sphingosine 1-phosphate), we found that cells sensed higher concentrations of S1P in the medullary cords than in the T cell zone and that the S1P transporter SPNS2 on lymphatic endothelial cells generated this gradient. Natural killer (NK) cells are located at the periphery of the lymph node, predominantly in the medulla, and we found that expression of SPNS2, expression of the S1P receptor S1PR5 on NK cells, and expression of the chemokine receptor CXCR4 were all required for NK cell localization during homeostasis and rapid production of interferon-γ by NK cells after challenge. Our findings elucidate the spatial cues for NK cell organization and reveal a previously unknown role for S1P in positioning cells within the medulla.

Design and pilot implementation of the Achieving Cancer Equity through Identification, Testing, and Screening (ACE-ITS) program in an urban underresourced population.

INTRODUCTION: The Achieving Cancer Equity through Identification, Testing, and Screening (ACE-ITS) program is a community-engaged framework to improve mammography maintenance and rates of genetic risk assessment, counseling, and testing using a multilevel approach that enhances patient navigation through mobile health and community education. METHODS: The ACE-ITS program is based on the National Institute of Minority Health and Health Disparities research framework focused on the individual (genetic testing, screening navigation) and community (community-based breast health education) levels and targeted to the biological- (genetic risk), behavioral- (mammography screening), sociocultural- (underserved Black and Hispanic women), and the health care system (patient navigation, automated text messages)-related domains. We further integrate the Practical Robust Implementation and Sustainability Model to describe our program implementation. RESULTS: In collaboration with genetic counselors and community partners, we created educational modules on mammography maintenance and genetic counseling/testing that have been incorporated into the navigator-led community education sessions. We also implemented a universal genetic risk assessment tool and automated text message reminders for repeat mammograms into our mammography navigation workflow. Through the ACE-ITS program implementation, we have collaboratively conducted 22 educational sessions and navigated 585 women to mammography screening over the 2020-2021 calendar years. From January to December 2021, we have also conducted genetic risk assessment on 292 women, of whom 7 have received genetic counseling/testing. CONCLUSIONS: We describe a multilevel, community-engaged quality improvement program designed to reduce screening-related disparities in Black and Hispanic women in our catchment area.

Stability and function of regulatory T cells expressing the transcription factor T-bet.

Adaptive immune responses are tailored to different types of pathogens through differentiation of naive CD4 T cells into functionally distinct subsets of effector T cells (T helper 1 (TH1), TH2, and TH17) defined by expression of the key transcription factors T-bet, GATA3, and RORγt, respectively. Regulatory T (Treg) cells comprise a distinct anti-inflammatory lineage specified by the X-linked transcription factor Foxp3 (refs 2, 3). Paradoxically, some activated Treg cells express the aforementioned effector CD4 T cell transcription factors, which have been suggested to provide Treg cells with enhanced suppressive capacity. Whether expression of these factors in Treg cells-as in effector T cells-is indicative of heterogeneity of functionally discrete and stable differentiation states, or conversely may be readily reversible, is unknown. Here we demonstrate that expression of the TH1-associated transcription factor T-bet in mouse Treg cells, induced at steady state and following infection, gradually becomes highly stable even under non-permissive conditions. Loss of function or elimination of T-bet-expressing Treg cells-but not of T-bet expression in Treg cells-resulted in severe TH1 autoimmunity. Conversely, following depletion of T-bet- Treg cells, the remaining T-bet+ cells specifically inhibited TH1 and CD8 T cell activation consistent with their co-localization with T-bet+ effector T cells. These results suggest that T-bet+ Treg cells have an essential immunosuppressive function and indicate that Treg cell functional heterogeneity is a critical feature of immunological tolerance.

Lymphatic endothelial S1P promotes mitochondrial function and survival in naive T cells.

Effective adaptive immune responses require a large repertoire of naive T cells that migrate throughout the body, rapidly identifying almost any foreign peptide. Because the production of T cells declines with age, naive T cells must be long-lived. However, it remains unclear how naive T cells survive for years while constantly travelling. The chemoattractant sphingosine 1-phosphate (S1P) guides T cell circulation among secondary lymphoid organs, including spleen, lymph nodes and Peyer's patches, where T cells search for antigens. The concentration of S1P is higher in circulatory fluids than in lymphoid organs, and the S1P1 receptor (S1P1R) directs the exit of T cells from the spleen into blood, and from lymph nodes and Peyer's patches into lymph. Here we show that S1P is essential not only for the circulation of naive T cells, but also for their survival. Using transgenic mouse models, we demonstrate that lymphatic endothelial cells support the survival of T cells by secreting S1P via the transporter SPNS2, that this S1P signals through S1P1R on T cells, and that the requirement for S1P1R is independent of the established role of the receptor in guiding exit from lymph nodes. S1P signalling maintains the mitochondrial content of naive T cells, providing cells with the energy to continue their constant migration. The S1P signalling pathway is being targeted therapeutically to inhibit autoreactive T cell trafficking, and these findings suggest that it may be possible simultaneously to target autoreactive or malignant cell survival.

Corrigendum: Stability and function of regulatory T cells expressing the transcription factor T-bet.

This corrects the article DOI: 10.1038/nature22360.

Advancing health equity: A qualitative study assessing barriers and facilitators of implementing hereditary breast and ovarian cancer risk screening tools in community-based organizations.

Genetic counseling and testing (GCT) inform cancer management for persons at risk for hereditary breast and ovarian cancer (HBOC). Community-based organizations (CBOs) may play a role in identifying at-risk Latinx individuals to connect them to GCT but data are lacking. Two academic centers and their four CBO partners planned to implement a validated questionnaire for HBOC risk screening ("HBOC risk screening tool"). This study aimed to assess CBO's preferences for HBOC risk screening tools, as well as the barriers and facilitators anticipated for future implementation. Pre-implementation focus groups were conducted with CBO's staff. Discussions centered on current practices to identify and refer at-risk patients. During the discussion, staff were asked to select one out of five validated HBOC risk screening tools to implement and to discuss anticipated barriers/facilitators for implementation. The four focus groups were coded and qualitative analyzed following the Consolidated Framework for Implementation Research (CFIR) and Health Equity domains. All CBOs chose the Family History Screen 7 (FHS-7). Participants (N = 35) highlighted how the FHS-7 was easy to adapt to better fit the target population and changing guidelines. They had positive attitudes toward implementing the screening tool, stressed how the culture of the organization positioned them to reach the target population, and noted barriers in different CFIR domains (e.g., low knowledge about HBOC and GCT referrals; scarce available resources). Participants pointed to barriers related to health equity domains including limited access to GCT and follow-up care for uninsured and underinsured populations, challenges obtaining accurate family history, and immigration-related barriers. CBOs highlighted the importance of partnering with other stakeholders to overcome barriers. Findings emphasize the need to develop multi-level implementation strategies to overcome barriers and leverage facilitators. This study can inform the development of implementation toolkits for CBOs to implement HBOC screening tools to advance health equity.

Confidence, Connection & Collaboration: Creating a Scalable Bias Reduction Improvement Coaching Train-the-Trainer Program to Mitigate Implicit Bias across a Medical Center.

Problem: Academic medical centers need to mitigate the negative effects of implicit bias with approaches that are empirically-based, scalable, sustainable, and specific to departmental needs. Guided by Kotter's Model of Change to create and sustain cultural change, we developed the Bias Reduction Improvement Coaching Program (BRIC), a two-year, train-the-trainer implicit bias coaching program designed to meet the increasing demand for bias training across a university medical center. Intervention: BRIC trained a cohort of faculty and staff as coaches during four quarterly training sessions in Year 1 that covered 1) the science of bias, 2) bias in selection and hiring, 3) bias in mentoring, and 4) bias in promotion, retention, and workplace culture. In Year 2, coaches attended two booster sessions and delivered at least two presentations. BRIC raises awareness of bias mitigation strategies in a scalable way by uniquely building capacity through department-level champions, providing programming that addresses the 'local context,' and setting a foundation for sustained institutional change. Context: In a U.S. academic medical center, 27 faculty and staff from 24 departments were trained as inaugural BRIC coaches. We assessed outcomes at multiple levels: BRIC coach outcomes (feedback on the training sessions; coach knowledge, attitudes, and skills), departmental-level outcomes (program attendee feedback, knowledge, and intentions) and institutional outcomes (activities to sustain change). Impact: After Year 1, coaches reported high satisfaction with BRIC and a statistically significant increase in self-efficacy in their abilities to recognize, mitigate, and teach about implicit bias. In Year 2, attendees at BRIC coach presentations reported an increase in bias mitigation knowledge, and the majority committed to taking follow-up action (e.g., taking an Implicit Association Test). Coaches also launched activities for sustaining change at the broader university and beyond. Lessons Learned: The BRIC Program indicates a high level of interest in receiving bias mitigation training, both among individuals who applied to be BRIC coaches and among presentation attendees. BRIC's initial success supports future expansion. The model appears scalable and sustainable; future efforts will formalize the emerging community of practice around bias mitigation and measure elements of on-going institutional culture change.

A culturally targeted video to promote genetic counseling in a community sample of at-risk US Latina women: The role of the concrete mindset.

Latina women, who are at increased risk of hereditary breast and ovarian cancer (HBOC), have lower use of genetic counseling and testing (GCT) than non-Hispanic White women. In a recent study, culturally targeted video improved psychosocial outcomes related to GCT. Additional analyses examine whether the culturally targeted video improved positive reactions in women who focus on difficulties (concrete mindset) versus women who focus on the final goals (abstract mindset). Participants (N = 32) completed surveys before and immediately after watching the video. The surveys measured attitudes, emotions, and women's mindset. Before watching the video, women with a concrete mindset reported more negative attitudes and negative emotions about GCT than women with an abstract mindset. After watching the video, women with a concrete mindset reported negative attitudes and feelings at levels comparable to those of women with an abstract mindset, reflecting a reduction in their negative attitudes and emotions. The sample size limits the power to find statistically significant differences. Results support the relevance of considering the audience's mindset in the development and testing of public health messages to promote the use of GCT.

Community research collaboration to develop a promotores-based hereditary breast cancer education program for Spanish-speaking Latinas.

Breast cancer (BC) is the most common cancer in Latinas and the leading cause of cancer death. Latinas tend to be diagnosed at later stages, receive poorer quality care and have a higher risk of mortality than non-Latina White (NLW) women. Among women with a genetic predisposition to hereditary BC, genetic counseling can be beneficial. Latinas participate in genetic counseling at lower rates than NLW women. The goal of this study was to develop comprehensive, culturally appropriate materials for community health educators (promotores)-led hereditary BC education program for Spanish-speaking Latinas. We developed the curriculum through feedback from 7 focus groups, with a total of 68 participants (35 promotores and 33 community members). We used a mixed-methods approach that relied on quantitative analysis of survey questions and qualitative content analysis of the focus groups transcripts. Pre and post promotores' training survey responses suggested improvement in the promotores' cancer-related knowledge. Themes that emerged from the qualitative analyses were (i) barriers to health education and/or care; (ii) importance of educating the Latino community about BC and genetics and (iii) role of the promotores. Future research will further evaluate the impact of the program in promotores' knowledge and community members' screening behaviors.

The role of psychosocial factors in Black women's self-efficacy in receiving genetic counseling and testing.

Higher self-efficacy in receiving genetic counseling and testing (GCT) has been associated with greater participation in GCT for women at risk of hereditary breast and ovarian cancer (HBOC), but little is known about correlates of self-efficacy in Black women eligible for GCT. The goal of this secondary analysis was to identify sociodemographic and psychosocial factors regarding GCT. Multivariable regression analysis was conducted to assess the relationship between self-efficacy and correlates of interest. Of the 100 Black women surveyed, most women had a college degree (64%), were employed (84%), and had health insurance (93%). In the multivariable model, greater self-efficacy was associated with more positive attitudes toward GCT (Β = 0.126; CI = 0.01 to 0.25; p = 0.039), greater confidence in the Genetic Information Nondiscrimination Act (GINA) (Β = 0.250; CI = 0.04 to 0.46; p = 0.019), and lower ratings of perceived difficulty obtaining GCT (Β = -0.219; CI = -0.46 to -0.10; p = 0.003). Community-level interventions to promote self-efficacy are needed that address perceived barriers to GCT, with the goals of increasing GINA Law awareness in the general public, increasing accessibility to genetic counseling (e.g., telemedicine), and promoting more positive attitudes about GCT.

Process evaluation of a culturally targeted video for Latinas at risk of hereditary breast and ovarian cancer.

This paper presents a process evaluation of a culturally targeted narrative video about hereditary breast and ovarian cancer (HBOC) for Latina women at risk for HBOC. Spanish-speaking Latina women at risk for HBOC participated in a single arm study (n = 40). Participants watched the video developed by the authors and responded to surveys. We used mixed methods to assess theoretical constructs that are hypothesized mediators of narrative interventions (i.e., transportation or engagement, identification with characters, emotions) and implementation outcomes (e.g., acceptability). Descriptive statistics summarized theoretical constructs and implementation outcomes. We conducted Mann-Whitney U tests to assess the differences in theoretical and implementation outcomes between participants who were affected versus. unaffected and participants with different levels of education and health literacy. We used the consensual qualitative research framework to analyze qualitative data. Participants' mean age was 47.1 years (SD = 9.48). Most participants were high school graduates or less (62.5%). Acceptability of the video was extremely high (Md = 10.0, IQR = 0.2, scale 1-10). Most (82.5%) suggested video dissemination be through social media. Participants were highly engaged (Md = 5.7, IQR = 1.5, scale 1-7), strongly identified with the main character (Md = 8.7, IQR = 2.6, scale 1-10), and reported experiencing mostly positive emotions (Md = 9.5, IQR = 2.8, scale 1-10). Participants with low health literacy and affected participants reported a significantly higher identification with the main character (p<.05). Qualitative data reinforced the quantitative findings. Women reported gaining knowledge, correcting misconceptions, and feeling empowered. Our culturally targeted video is highly acceptable and targets mechanisms of behavior change for narrative interventions. The video is easily disseminable and can be used as an education tool for patients including affected and unaffected women and patients with different education and health literacy levels. Future studies should test the impact of the video in enhancing genetic counseling and testing uptake.

Sociodemographic, clinical, psychosocial, and healthcare-related factors associated with beliefs about adjuvant endocrine therapy among breast cancer survivors.

OBJECTIVE: Adjuvant endocrine therapy (AET) reduces the risk of recurrence and mortality in women with hormone receptor-positive breast cancer. However, adherence to AET remains suboptimal. Women's beliefs about medication have been associated with medication adherence. The purpose of this study was to identify multilevel factors associated with women's beliefs about AET. METHODS: Beliefs about AET, measured using the Belief about Medicines Questionnaire (BMQ), sociodemographic (e.g., age), psychosocial (e.g., religiosity), and healthcare factors (e.g., patient-provider communication), were collected via survey. Clinical data were abstracted from medical records. Two stepwise regression analyses models were performed to assess relationships between variables and necessity and concern beliefs. RESULTS: In our sample of 572 women, mean BMQ concern score was 11.19 and mean necessity score was 13.85 (range 5-20). In the regression models, higher ratings of patient-provider communication were associated with lower concern and higher necessity beliefs. Higher concern beliefs were related to more AET-related symptoms (Β = 0.08; 95% CI 0.06 to 0.10; p < 0.001), lower patient satisfaction (Β = - 0.07; 95% CI - 0.09 to - 0.04; p < 0.001), and higher religiosity (Β = 0.05; 95% CI 0.01 to 0.08; p = 0.007). Higher necessity beliefs were associated with prior chemotherapy use (Β = 0.11; 95% CI 0.06 to 0.16; p < 0.005) and less education (Β = 1.00; 95% CI 0.27 to 1.73; p = 0.008). CONCLUSIONS: Modifiable factors are related to women's AET beliefs. Healthcare interactions may play a key role with regard to shaping women's beliefs about their AET medication.

Latinas' knowledge of and experiences with genetic cancer risk assessment: Barriers and facilitators.

Disparities in genetic cancer risk assessment (GCRA) uptake persist between Latinas and Non-Hispanic Whites. This study utilized a mental model approach to interview 20 Latinas (10 affected, 10 unaffected) at increased risk for hereditary breast and ovarian cancer (HBOC). Participants were asked about their knowledge and perceptions of GCRA, HBOC, risk, benefits, motivators, barriers, challenges, and experiences with GCRA. Using the Consensual Qualitative Analysis Framework, two authors independently coded the interviews and applied the final codes upon consensus. Additionally, interviews were coded to identify whether participants spontaneously brought up certain topics without a prompt. Findings identified multiple barriers and facilitators to GCRA uptake in this population, including patient level psychosocial/cultural factors (e.g., limited knowledge, worry about relatives' risk) and healthcare system factors (e.g., receiving no referrals). There were notable differences in awareness and knowledge between affected and unaffected women (e.g., genetic testing awareness), as well as knowledge gaps that were evident in both groups (e.g., age of diagnosis as a risk factor). To reduce disparities in GCRA uptake, interventions should address identified facilitators and barriers. Differences in knowledge and awareness between affected and unaffected women support the development of targeted interventions that address specific knowledge gaps. This study was registered in ClinicalTrials.gov (NCT03075540) by Alejandra Hurtado de Mendoza, Ph.D.

Applying the theory of planned behavior to examine adjuvant endocrine therapy adherence intentions.

OBJECTIVE: Adherence to adjuvant endocrine therapy (AET) in breast cancer survivors is suboptimal. Using the theory of planned behavior (TPB), this study aimed to identify the strongest predictors from the TPB of AET intentions and past behavior and assessed whether ambivalence and anticipatory emotions increased the predictive capacity of TPB. METHODS: Two hundred eighty women diagnosed with hormone positive (HR+) breast cancer who filled at least one prescription of AET responded to a survey measuring TPB constructs, attitudinal ambivalence, and anticipatory emotions. The outcomes were intentions to adhere to AET and past medication adherence (previous 2 weeks). RESULTS: The TPB explained 66% of intentions to adhere to AET (P < 0.001). Ambivalence did not improve the TPB model's predictive value. When emotions were included with TPB, the model explained 70% of adherence intentions F11,226  = 52.84, P < 0.001 (R2c  = .70). This increase of 4% in predictability was statistically significant (ΔR2  = 0.04), F6, 226  = 7.90, P < 0.001. Women who self-reported nonadherence in the past 2 weeks differed significantly in the TPB variables, ambivalence, and anticipatory emotions from adherent women. Nonadherent participants reported lower-future intentions to adhere F1, 236  = 5.63, P = 0.018. CONCLUSIONS: Results suggest key concepts, such as anticipatory positive emotions that should be addressed in future interventions to enhance AET adherence and survivorship.

Psychometric Properties of the Medical Mistrust Index (MMI) in Latina Immigrants.

Medical mistrust measures have not been validated in Latino immigrants. This study examined the psychometric properties of the Medical Mistrust Index and its association with health care satisfaction in a sample of Latina immigrants. Participants were 168 self-identified Latinas ≥40 years old. Women were recruited from three Latino-serving health clinics and through a Latino radio program. A bilingual interviewer administered the Medical Mistrust Index in Spanish along with items pertaining to sociodemographic and health care factors. Principal component extraction method was used to evaluate internal consistency reliability to examine Medical Mistrust Index underlying factors. Construct validity was assessed by analyzing the relationship between the Medical Mistrust Index with three related measures (racism, discrimination, trust in doctors). To assess the criterion validity of the Medical Mistrust Index, a logistic regression model examined whether medical mistrust was associated with Latina women's satisfaction with health care controlling for sociodemographic and health care factors. Participants were 51 years old on average, around half had completed High school or less and were uninsured. Most were monolingual Spanish speakers. Two factors: competence and suspicion explained 40% of the total Medical Mistrust Index variance. Internal consistency was favorable and construct validity was supported. Results support the reliability and validity of the Medical Mistrust Index and its association with Latina's satisfaction with health care.

Sentiment Analysis of an Online Breast Cancer Support Group: Communicating about Tamoxifen.

A better understanding of the breast cancer online narrative is important for a clearer conceptualizing of the role of online platforms in mediating health-related support. Sentiment analysis was conducted on a breast cancer online support group regarding Tamoxifen to understand users' emotions and opinions. This analysis was then contextualized within online social support literature. Out of the 498 users, the most active users were 80% more positive than least active users, while least active users were 48% more negative than most active ones; both differences were statistically significant. The higher the stage of cancer a user had, the less likelihood that she would have posted, and if she were to post, the post would have focused on her side effects and the anxiety/sadness that tailgates those side effects. The lower the stage of cancer a user had, the more likelihood that she would have posted, additionally remained active on the forum, and encouraged more (online) social support. This finding suggests that the online support platform may provide a context that exacerbates support for like-minded users where stronger ties are created around a specific sentiment within the community with less connection from those with dissimilar sentiments to the dominant group.

Understanding Breast Cancer Survivors' Beliefs and Concerns About Adjuvant Hormonal Therapy: Promoting Adherence.

Adjuvant hormonal therapy is recommended for women with hormone receptor (HR)-positive breast cancer. Though critical, many patients are non-adherent to this therapy. Few scales have been developed to specifically address beliefs about adjuvant hormonal therapy. This study explores the clarity and relevance of the Beliefs about Medicine Questionnaire (BMQ) in the context of adherence behaviors to hormonal therapy in Black and White breast cancer survivors. We recruited women diagnosed with HR-positive cancer from the Washington, DC, area. An interviewer administered a standardized survey and conducted a cognitive interview. Participants rated the BMQ across three areas: relevance, difficulty, and clarity. We coded whether the comments identified item level issues: limited applicability, unclear reference, unclear perspective, or wording or tone. In-depth interviews were conducted with women who prematurely discontinued hormone therapy. The sample (n = 30) was equally split between Black and White survivors. On average, women were 57.9 years old (SD = 9.0). Overall 77% rated scale as relevant. Cognitive interviews revealed areas of perceived limited acceptability such as the notion of becoming too dependent or the notion of becoming worse if not taking the medication. Women who discontinued hormonal therapy (n = 2) felt ambivalent towards hormonal therapy as they reported having both positive and negative beliefs about the medication. Our study findings suggest new areas for further research and instrument development to accurately measure self-reported beliefs about hormonal therapy by HR-positive breast cancer survivors.

The Bacterial Community Structure and Dynamics of Carbon and Nitrogen when Maize (Zea mays L.) and Its Neutral Detergent Fibre Were Added to Soil from Zimbabwe with Contrasting Management Practices.

Water infiltration, soil carbon content, aggregate stability and yields increased in conservation agriculture practices compared to conventionally ploughed control treatments at the Henderson research station near Mazowe (Zimbabwe). How these changes in soil characteristics affect the bacterial community structure and the bacteria involved in the degradation of applied organic material remains unanswered. Soil was sampled from three agricultural systems at Henderson, i.e. (1) conventional mouldboard ploughing with continuous maize (conventional tillage), (2) direct seeding with a Fitarelli jab planter and continuous maize (direct seeding with continuous maize) and (3) direct seeding with a Fitarelli jab planter with rotation of maize sunn hemp (direct seeding with crop rotation). Soil was amended with young maize plants or their neutral detergent fibre (NDF) and incubated aerobically for 56 days, while C and N mineralization and the bacterial community structure were monitored. Bacillus (Bacillales), Micrococcaceae (Actinomycetales) and phylotypes belonging to the Pseudomonadales were first degraders of the applied maize plants. At day 3, Streptomyces (Actinomycetales), Chitinophagaceae ([Saprospirales]) and Dyella (Xanthomonadales) participated in the degradation of the applied maize and at day 7 Oxalobacteraceae (Burkholderiales). Phylotypes belonging to Halomonas (Oceanospirillales) were the first degraders of NDF and were replaced by Phenylobacterium (Caulobacterales) and phylotypes belonging to Pseudomonadales at day 3. Afterwards, similar bacterial groups were favoured by application of NDF as they were by the application of maize plants, but there were also clear differences. Phylotypes belonging to the Micrococcaceae and Bacillus did not participate in the degradation of NDF or its metabolic products, while phylotypes belonging to the Acidobacteriaceae participated in the degradation of NDF but not in that of maize plants. It was found that agricultural practices had a limited effect on the bacterial community structure, but application of organic material altered it substantially.