Summary Prospectus
February 1, 2012

Loomis Sayles Investment Grade Bond Fund Ticker Symbol: Class A (LIGRX), Class B (LGBBX), Class C (LGBCX), Class Y (LSIIX) and Admin Class (LIGAX)

Before you invest, you may want to review the Fund’s Prospectus, which contains more information about the Fund and its risks. You can find the Fund’s Prospectus and other information about the Fund online at ngam.natixis.com/funddocuments. You can also get this information at no cost by calling 800-225-5478 or by sending an e-mail request to NatixisFunds@ngam.natixis.com. The Fund’s Prospectus and Statement of Additional Information, each dated February 1, 2012 are incorporated by reference into this Summary Prospectus.

Investment Goal The Fund seeks high total investment return through a combination of current income and capital appreciation. Fund Fees & Expenses The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Fund Complex. More information about these and other discounts is available from your financial professional and in the section “How Sales Charges Are Calculated” on page 59 of the Prospectus and on page 106 in the section “Reduced Sales Charges” of the Statement of Additional Information (“SAI”).

Shareholder Fees(fees paid directly from your investment)	Class A	Class B	Class C	Class Y	Admin Class
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	4.50%	None	None	None	None
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	None	5.00%	1.00%	None	None
Redemption fees	None	None	None	None	None

Annual Fund Operating Expenses(expenses that you pay each year as a percentage of the value of your investment)	Class A	Class B	Class C	Class Y	Admin Class
Management fees	0.40%	0.40%	0.40%	0.40%	0.40%
Distribution and/or service (12b-1) fees	0.25%	1.00%	1.00%	0.00%	0.25%
Other expenses*	0.16%	0.16%	0.16%	0.16%	0.42%
Total annual fund operating expenses	0.81%	1.56%	1.56%	0.56%	1.07%
Fee waiver and/or expense reimbursement1	0.00%	0.00%	0.00%	0.00%	0.00%
Total annual fund operating expenses after fee waiver and/or expense reimbursement	0.81%	1.56%	1.56%	0.56%	1.07%

Example This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods (except where indicated). The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

	Class A	Class B		Class C		Class Y	Admin Class
		If shares are redeemed	If shares are not redeemed	If shares are redeemed	If shares are not redeemed
1 year	$529	$659	$159	$259	$159	$57	$109
3 years	$697	$793	$493	$493	$493	$179	$340
5 years	$879	$1,050	$850	$850	$850	$313	$590
10 years	$1,407	$1,655	$1,655	$1,856	$1,856	$701	$1,306

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*

Other expenses include an administrative services fee of 0.25% for Admin Class shares.

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Loomis, Sayles & Company, L.P. (“Loomis Sayles” or the “Adviser”) has given a binding contractual undertaking to the Fund to limit the amount of the Fund’s total annual fund operating expenses to 0.95%, 1.70%, 1.70%, 0.70%, and 1.20% of the Fund’s average daily net assets for Class A, B, C, and Y and Admin Class shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2013 and may be terminated before then only with the consent of the Fund’s Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below 0.95%, 1.70%, 1.70%, 0.70%, and 1.20% of the Fund’s average daily net assets for Class A, B, C and Y and Admin Class shares, respectively. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

Portfolio Turnover The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes for you if your Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. During its most recently ended fiscal year, the Fund’s portfolio turnover rate was 19% of the average value of its portfolio. Investments, Risks and Performance Principal Investment Strategies Under normal market conditions, the Fund will invest at least 80% of its net assets (plus any borrowings made for investment purposes) in investment-grade fixed-income securities (for example, bonds and other investments that Loomis Sayles believes have similar economic characteristics, such as notes, debentures and loans). “Investment-grade” securities are those securities that are rated as such at the time of purchase by at least one of the three major rating agencies —  Moody’s Investors Service, Inc. (“Moody’s”), Fitch Investor Services, Inc. (“Fitch”) or Standard & Poor’s Ratings Group (“S&P”) or, if unrated, are determined by the Adviser to be of comparable quality. Although the Fund invests primarily in investment-grade fixed-income securities, it may invest up to 10% of its assets in below investment-grade fixed-income securities (also known as “junk bonds”). The Fund has the flexibility to invest up to 10% of its assets in equity securities (such as common stocks, preferred stocks and investment companies), but will limit its investments in common stocks to 5% of its assets. Below investment-grade fixed-income securities are rated below investment-grade quality (i.e., none of the three major rating agencies (Moody’s, Fitch or S&P) have rated the securities in one of their top four ratings categories) or, if unrated, are determined by the Adviser to be of comparable quality. There is no minimum rating for the securities in which the Fund may invest. The Fund may invest in fixed income-securities of any maturity. In deciding which securities to buy and sell, the Adviser will consider, among other things, the financial strength of the issuer, current interest rates, current valuations, the Adviser’s expectations regarding future changes in interest rates and comparisons of the level of risk associated with particular investments with the Adviser’s expectations concerning the potential return of those investments. Three themes typically drive the Fund’s investment approach. First, the Adviser generally seeks fixed-income securities of issuers whose credit profiles it believes are improving. Second, the Fund makes significant use of non-market-related securities, which are securities that may not have a direct correlation with changes in interest rates. The Adviser believes that the Fund may generate positive returns by having a portion of the Fund’s assets invested in non-market-related securities, rather than by relying primarily on changes in interest rates to produce returns for the Fund. Third, the Adviser analyzes different sectors of the economy and differences in the yields (“spreads”) of various fixed-income securities in an effort to find securities that it believes may produce attractive returns for the Fund in comparison to their risk. The Adviser generally prefers securities that are protected against calls (early redemption by the issuer). In connection with its principal investment strategies, the Fund may also invest any portion of its assets in securities of Canadian issuers and up to 20% of its assets in securities of other foreign issuers, including emerging markets securities. The Fund may also invest in obligations of supranational entities without limit ( e.g. , the World Bank), corporate securities, U.S. government securities, commercial paper, zero-coupon securities, mortgage-backed securities, including mortgage dollar rolls, stripped mortgage-backed securities and collateralized mortgage obligations and other asset-backed securities, when-issued securities, convertible securities, Rule 144A securities and structured notes. The Fund may also engage in foreign currency hedging transactions and swap transactions (including credit default swaps) for hedging or investment purposes. The Adviser may elect not to hedge currency risk, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Except as provided above, the Fund is not limited in the percentage of its assets that it may invest in these instruments. Principal Risks The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund. Below Investment-Grade Fixed-Income Securities Risk: This is the risk that the Fund’s investments in below investment-grade fixed-income securities, also known as “junk bonds,” may be subject to greater risks than other fixed-income securities, including being subject to greater levels of interest rate risk, credit risk (including a greater risk of default) and liquidity risk. The ability of the issuer to make principal and interest payments is predominantly speculative for below investment-grade fixed-income securities. Credit Risk: Credit risk is the risk that the issuer or the guarantor of a fixed-income security, or the counterparty to a derivatives or other transaction, will be unable or unwilling to make timely payments of interest or principal or to otherwise honor its obligations.

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Currency Risk: Fluctuations in the exchange rates between different currencies may negatively affect an investment. The Fund may elect not to hedge currency risk, or may hedge such risk imperfectly, which may cause the Fund to incur losses that would not have been incurred had the risk been hedged. Derivatives Risk: Derivatives are subject to changes in the value of the underlying asset or indices on which such transactions are based. There is no guarantee that the use of derivatives will be effective or that suitable transactions will be available. Even a small investment in derivatives may give rise to leverage risk and can have a significant impact on the Fund’s exposure to securities markets values, interest rates or currency exchange rates. It is possible that the Fund’s liquid assets may be insufficient to support its obligations under its derivatives positions. The use of derivatives for other than hedging purposes may be considered a speculative activity, and involves greater risks than are involved in hedging. The use of derivatives may cause the Fund to incur losses greater than those which would have occurred had derivatives not been used. The Fund’s use of derivatives such as forward currency contracts, structured notes, and swap transactions involves other risks, such as the credit risk relating to the other party to a derivative contract (which is greater for forward currency contracts, swaps, and other over-the-counter traded derivatives), the risk of difficulties in pricing and valuation, the risk that changes in the value of a derivative may not correlate perfectly with relevant assets, rates or indices, liquidity risk, allocation risk and the risk of losing more than the initial margin required to initiate derivatives positions. There is also the risk that the Fund may be unable to terminate or sell a derivatives position at an advantageous time or price. Moreover, a number of broker-dealers and other financial institutions have recently experienced extreme financial difficulty, sometimes resulting in bankruptcy of the institution. Although Loomis Sayles monitors the creditworthiness of the Fund’s derivative counterparties, there can be no assurance that the Fund’s derivative counterparties will not experience similar financial difficulties, possibly resulting in losses to the Fund. Emerging Markets Risk: Investing in emerging markets companies, which may be smaller and have shorter operating histories than companies in developed markets, involves risks in addition to, and greater than, those generally associated with investing in companies in developed foreign markets. The extent of economic development, political stability, market depth, infrastructure, capitalization and regulatory oversight in emerging market economies is generally less than in more developed markets. Equity Securities Risk: The value of the Fund’s investments in equity securities is subject to unpredictable declines in the value of individual securities and periods of below-average performance in individual securities or in the equity market as a whole. In the event an issuer is liquidated or declares bankruptcy, the claims of owners of the issuer’s bonds and preferred stock generally take precedence over the claims of those who own common stock. Fixed-Income Securities Risk: Fixed-income securities are subject to credit risk, interest rate risk and liquidity risk. You may lose money on your investment due to unpredictable drops in a security’s value or periods of below-average performance in a given security or in the securities market as a whole. Below investment-grade fixed-income securities may be subject to these risks to a greater extent than other fixed-income securities. These securities are considered predominantly speculative with respect to the issuer’s continuing ability to make principal and interest payments. Zero-coupon bonds may be subject to these risks to a greater extent than other fixed-income securities. Rule 144A securities and structured notes may be more illiquid than other fixed-income securities. In addition, an economic downturn or period of rising interest rates could adversely affect the market of these securities and reduce a Fund’s ability to sell them. Foreign Securities Risk: Investments in foreign securities may be subject to greater political, economic, environmental, credit and information risks. The Fund’s investments in foreign securities are also subject to foreign currency fluctuations. Foreign securities may be subject to higher volatility than U.S. securities, varying degrees of regulation and limited liquidity. Interest Rate Risk: Changes in interest rates may cause the value of the Fund’s investments to decrease. Generally, the value of fixed-income securities rises when prevailing interest rates fall and falls when interest rates rise. A period of low interest rates may cause the Fund to have a low or negative yield, potentially reducing the value of your investment. The value of zero-coupon bonds may be more sensitive to fluctuations in interest rates than other fixed income securities. Issuer Risk: The value of the Fund’s investments may decline for a number of reasons that directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer’s goods and services. Leverage Risk: Use of derivative instruments may involve leverage. Leverage is the risk associated with securities or practices that multiply small index, market or asset price movements into larger changes in value. To the extent that the Fund uses a derivative for purposes other than as a hedge, or if the Fund hedges imperfectly, the Fund is directly exposed to the risks of that derivative and any loss generated by the derivative will not be offset by a gain. The use of leverage increases the impact of gains and losses on a fund’s returns, and may lead to significant losses if investments are not successful. However, the Adviser will attempt to ensure that at all times the Fund has sufficient liquid assets to enable it to satisfy its obligations under its derivative contracts. Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell, possibly preventing the Fund from selling these illiquid securities at an advantageous price or time. A lack of liquidity also may cause the value of investments to decline. Illiquid investments also may be difficult to value. Management Risk: A strategy used by the Fund’s portfolio managers may fail to produce the intended result. Market Risk: The market value of a security will move up and down, sometimes rapidly and unpredictably, based upon a change in an issuer’s financial condition, as well as overall market and economic conditions.

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Mortgage-Related and Asset-Backed Securities Risk: In addition to the risks associated with investments in fixed-income securities generally (for example, credit, liquidity and valuation risk), mortgage-related and asset-backed securities are subject to the risks of the mortgages and assets underlying the securities as well as prepayment risk, the risk that the securities may be prepaid and result in the reinvestment of the prepaid amounts in securities with lower yields than the prepaid obligations. Conversely, there is a risk that an unexpected rise in interest rates will extend the life of a mortgage-related or asset-backed security beyond the expected prepayment time, typically reducing the security’s value. The Fund also may incur a loss when there is a prepayment of securities that were purchased at a premium. The Fund’s investments in other asset-backed securities are subject to risks similar to those associated with mortgage-related securities, as well as additional risks associated with the nature of the assets and the servicing of those assets. Risk/Return Bar Chart and Table The bar chart and table shown below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s performance from year-to-year and by showing how the Fund’s average annual returns for the one-year, five-year and ten-year periods compare to those of a broad measure of market performance. The Fund’s past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available online at ngam.natixis.com and/or by calling the Fund toll-free at 800-225-5478. The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund’s shares. A sales charge will reduce your return. Total Returns for Class Y Shares

	Highest Quarterly Return: Second Quarter 2009, 12.65%
	Lowest Quarterly Return: Third Quarter 2008, -7.19%

Class B total returns in the table below do not reflect the automatic conversion of Class B shares to Class A shares after eight years.

Average Annual Total Returns (for the periods ended December 31, 2011)	Past 1 Year	Past 5 Years	Past 10 Years
Loomis Sayles Investment Grade Bond Fund Class Y – Return Before Taxes	5.08%	7.75%	8.88%
Return After Taxes on Distributions	2.85%	5.45%	6.43%
Return After Taxes on Distributions & Sale of Fund Shares	3.43%	5.30%	6.25%
Class A – Return Before Taxes	0.12%	6.50%	8.08%
Class B – Return Before Taxes	-0.79%	6.27%	7.67%
Class C – Return Before Taxes	3.09%	6.67%	7.71%
Admin Class – Return Before Taxes	4.52%	7.05%	8.05%
Barclays Capital U.S. Government/Credit Bond Index	8.74%	6.55%	5.85%

The returns shown in the table for Class A shares prior to September 15, 2003 are those of Retail Class shares, which were redesignated as Class A shares, restated to reflect the sales loads of Class A shares. For the period from January 1, 2002 to January 31, 2002, during which time Retail Class shares were not outstanding, performance is that of Institutional Class shares, restated to reflect the higher net expenses and sales loads of Class A shares. Prior to the inception of Class B and Class C shares (September 12, 2003), performance is that of Institutional Class shares, which were redesignated as Class Y shares, restated to reflect the higher net expenses and sales loads of Class B and Class C shares, respectively. Prior to the inception of Admin Class shares (February 1, 2010), performance is that of Class A shares, restated to reflect the higher net expenses of Admin Class shares. Prior to February 1, 2012, Class A, B and C shares were offered in a separate prospectus and given that Class A, B and C shares are now offered in this multi-class prospectus, Total Return, Return After Taxes on Distributions and Return After Taxes on Distributions & Sale of Fund Shares are now presented for Class Y shares.

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After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for only one class of the Fund. After-tax returns for the other classes of the Fund will vary. Management Investment Adviser Loomis, Sayles & Company, L.P. Portfolio Managers Matthew J. Eagan, CFA, Vice President of the Adviser, served as associate portfolio manager of the Fund from 2006 to 2012 and has served as portfolio manager of the Fund since 2012. Daniel J. Fuss, CFA, Vice Chairman, Director and Managing Partner of the Adviser, served as co-portfolio manager of the Fund from 1996 to 2012 and has served as portfolio manager of the Fund since 2012. Kathleen C. Gaffney, CFA, Vice President of the Adviser, served as associate portfolio manager of the Fund from 2006 to 2012 and has served as portfolio manager of the Fund since 2012. Elaine M. Stokes, Vice President of the Adviser, served as an associate portfolio manager of the Fund from 2006 to 2012 and has served as portfolio manager of the Fund since 2012. Purchase and Sale of Fund Shares Class A and C Shares The following chart shows the investment minimums for various types of accounts:

Type of Account	Minimum Initial Purchase	Minimum Subsequent Purchase
Any account other than those listed below	$2,500	$100
For shareholders participating in Natixis Funds’ Investment Builder Program	$1,000	$50
For Traditional IRA, Roth IRA, Rollover IRA, SEP-IRA and Keogh plans using the Natixis Funds’ prototype document (direct accounts, not held through intermediary)	$1,000	$100
Coverdell Education Savings Accounts	$500	$100

Class B Shares Class B Shares of the Fund are not currently offered for sale. Class Y Shares Class Y shares of the Fund may be purchased by the following entities at the following investment minimums. A minimum initial investment of $100,000 and the minimum subsequent investment of $100 for:

• Other mutual funds, endowments, foundations, bank trust departments or trust companies.

There is no initial or subsequent investment minimum for:

• Wrap Fee Programs of certain broker-dealers, the advisers or NGAM Distribution, L.P. (the “Distributor”). Such wrap fee programs may be subject to additional or different conditions, including a wrap account fee. Each broker-dealer is responsible for transmitting to its customer a schedule of fees and other information regarding any such conditions.
• Retirement Plans such as 401(a), 401(k) or 457 plans.
• Certain Individual Retirement Accounts if the amounts invested represent rollover distributions from investments by any of the retirement plans invested in the Fund as set forth above.
• Registered Investment Advisers investing on behalf of clients in exchange for an advisory, management or consulting fee.
• Fund Trustees, former Fund trustees, employees of affiliates of the Natixis Funds and other individuals who are affiliated with any Natixis Fund (this also applies to any spouse, parents, children, siblings, grandparents, grandchildren and in-laws of those mentioned) and Natixis affiliate employee benefit plans.
  

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Due to operational limitations at your financial intermediary, certain wrap fee programs, retirement plans, individual retirement accounts and accounts of registered investment advisers may be subject to the investment minimums described above. Please consult your financial representative for more information. At the discretion of Loomis Sayles, employees and clients of Loomis Sayles may purchase Class Y shares of the Fund below the stated minimums. At the discretion of NGAM Advisors, L.P. (“NGAM Advisors”), clients of NGAM Advisors and its affiliates may purchase Class Y shares of the Fund below the stated minimums. Admin Class Shares Admin Class shares of the Fund are intended primarily for qualified retirement plans held in an omnibus fashion and are not appropriate for individual investors. Admin Class shares of the Fund require no minimum initial or subsequent investment. The Fund’s shares are available for purchase (and are redeemable on any business day) through your investment dealer, directly from the Fund by writing to the Fund at Natixis Funds, P.O. Box 219579, Kansas City, MO 64121-9579, by exchange, by wire, by internet at ngam.natixis.com, through the Automated Clearing House system, or, in the case of redemptions, by telephone at 800-225-5478 or by the Systematic Withdrawal Plan. Tax Information Fund distributions are generally taxable to you as ordinary income or capital gains, except for distributions to retirement plans and other investors that qualify for tax-exempt treatment under U.S. federal income tax law generally. Investments in such tax-advantaged plans will generally be taxed only upon withdrawal of monies from the tax-exempt arrangement. Payments to Broker-Dealers and Other Financial Intermediaries If you purchase shares of the Fund through a broker-dealer or other financial intermediary (such as a bank), the Fund and its related companies may pay the intermediary for the sale of the Fund shares and related services. These payments may create a conflict of interest by influencing the broker-dealer or other intermediary and your salesperson to recommend the Fund over another investment. Ask your salesperson or visit your financial intermediary’s website for more information.

UIG77-0212

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